To clone or to mod...THAT is the question.

Generally, the mod items in a mic are the capsule, the transformers, caps, etc. These happen to be the majority of the parts in the mic, besides the body.

I guess what I'm saying is that to do a good U87, you'd be gutting a donor down to the body, and then putting your own capsule, PCB, caps, transformer, etc in it. Might just be easier to get a kit for your first build. There is plenty to go wrong trying to go it on your own.

Dany Bouchard's U87 PCBs have been the basis of many successful clone builds...you can view the options here on his site, with links for the necessary metalwork and components:
vintagemicrophonepcbkit.com/DU87.html

High-quality body/headbasket by Chunger:
store.studio939.com/product/syt-5-microphone-body-kit

High-quality made-in-USA capsules by Eric Heiserman:
groupdiy.com/index.php?topic=49859.0

Cinemag transformers:
store.studio939.com/product/ami-microphone-transformers

U87 clone build threads:
groupdiy.com/index.php?topic=48030.0
groupdiy.com/index.php?topic=56983.msg726336#new

First time? Microphone-parts is the easy route, pictures, step by step instructions, no theory required.

When you become an expert, you can make your own from scratch.

This wouldn't be my first DIY - I feel pretty comfortable building a VP28 or a Hairball for example - but it would be the first mic. I absolutely agree that a complete kit really would be the way to go, nothing wrong with the easy route from where I sit...unless the overall quality of the mic somehow suffers as a result. If what I'd be building was just going to be a compromise I think I'd just as soon buy an off-the-rack mic.
I would even be ok with a kit that featured everything you needed for the build except the capsule and tranny - since those items are going to lend themselves more to personal preference and may very well get immediately or eventually switched out for alternatives.

It is interesting that you mentioned Microphone Parts, they're kind why I was wondering if it would make more sense to modify something pre-existing. Looking at the Microphone Parts website it doesn't look as if they actually offer an 87 kit these days. The Linear 87 kit is listed there, but as a discontinued product and everything else on the site seems to focus either on modification kits for pre-existing, prosumer mics or individual capsules (am I missing something? ).

I've looked at the vintagemicrophonepcbkit and that seems to lead in some tempting directions but it does leave me asking myself a few questions: How accurate is the BOM? Do I need to make any substitutions to what's listed on it? (I'm ok with spending a bit more to get the most optimum components for the build...as long as I know what to get)  Is there anything I REALLY need that isn't on it? How robust is the SYT-5 body? and, of course, what's the difference between the L, M and T variants and which is right for me?

The upshot is that the sourcing choices are something I really only need to get right once, after that it's just repeating the same steps. Trouble is I'd like to get the recipe right the first time!

Go to Groupdiy.com
There is a lot of build threads there. Some Step by step coloring books.
I've built over 25 mics and that's where I got my start.

here ya go, i wouldn't buy a single thing from that scumbag....
realgearonline.com/post/16839/thread

Now ya see, that's the kind of sleazy, deal-breaking stuff I'm talking about. I'll never understand why some schmucks put so much energy into scamming people; it would be a lot less energy to simply do things right in the first place and conduct an ethical business. It's like Wile E. Coyote and his absurd ACME contraptions. Oh well; cross that one off the list.

So I'll raise the white flag in the search for a soup-to-nuts kit...let me see if I can get my head around an a-la-carte approach and maybe you folks can tell me what y'all think:

I'll start off with SYT-5 gen 2 microphone body kit from Studio 939

Then the D-U87L Large PCB and  the switch PCB from Vintagemicrophonepcbkit.com (and I guess the Styroflex Capacitor Kit too?)

The Mouser BOM for the D-U87L

And of course the fun stuff;
Transformer - maybe an AMI T-13 or Cinemag CM-13113 (or does it make more sense to go with a T-14 or CM-13114?)

Capsule - Need some recommendations here - I think I'd like to stick with a K87 type of capsule but WHICH ONE? For the moment let's say TSKGUY's HK87

Does it seem like I'm forgetting anything? Any better choices for components I should check out? 

Very cool. Judging from what I've been reading it sounds like it should be a really good choice right out of the gate. Is it generally a long wait for any of his capsules? I'd like to be able to time it so everything arrives more or less at the same time.

The problem with Hendrix and ur stuff is, it's so over the top, when u try to copy it, it ALL sounds like mistakes! I've tried both 8)
(but I have certainly never tried to copy something to sell!)

I don't deal with MM anymore.  First, for the ethical reasons, second because I purchased a mic from them and received it with a faulty shockmount, torn foam in the case and a dented head grill.  I tried to contact them several times through email, ebay and facebook.  Never got a reply (left a comment on FB, they deleted it!)

I can't speak to the capsules, as I never used them.  I understand that you can no longer buy the kits without the complete set of components.  That makes the option of MM more expensive than sourcing your own if you want other components.

The body is a chinese body that does the job, but if I were you, I'd just get the whole kit from ioaudio.  Probably be around the same price in the end, looks more authentic, built better and you'll be supporting the real DIY community.

Okay, time for a little update.
I pulled the trigger on all of the stuff on the 18th. So far I've only received the Mouser components, everything else is backed up - but I have to admit I'm getting pretty psyched. It's looking like I might not actually see the other parts for a little while yet so I might have to do another build to take my mind off it; damn that urge for instant gratification!
 
I think that might be the reason I was originally hoping to find a cohesive kit...now I have to feel like a kid a week before Christmas for another month or so!