Cassave

RofS;

I had exactly the same thing happen except my MA2s had badly worn thinned sidewalls but no eyelet cracking.
I replaced only the rims with TB14s (love'em I've got two wheelsets built up with them.)
I did the tandem masking tape, swap one spoke at a time thing.
No problems with running out of thread.
You should be fine, in fact the proper thread engagement is to the top of the nipple according to Wheelsmith.
You'll likely end up right about there.

If you haven't built TB14s, all of mine camera came out of the box dead round and flat, makes for an easy build.

Edit: Oh, just noticed you've built TB14s before........