NEMA 34 to NEMA 42

I just got a Wells-Index CNC 700 and I'm looking into converting it to
servos.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7511611969&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
That's the ebay listing of some NEMA-34 frame servos that would be just
about perfect. I know I could go cheaper by modifying surplus treadmill
motors or by keeping a watchful eye on ebay, but these look like they're
more or less turn-key (a huge plus). Anything I should know about them?

The problem is that the Wells machine is coming with NEMA-42 steppers in
place. What's involved in adapting the 34 frame motors to the 42
mount? I looked up the spec sheets on the two, there are different hole
patterns (2.875" square, 34; 3.5" square, 42) and the shaft diameters
are different (.5" vs .625").

Over the next couple months I'll probably end up submitting all sorts of
other questions, I'd like to have this thing finished by sometime this
summer. Sometime next week I'll setup a website and post pictures. My
plan of attack at the moment is EMC -> pico-systems boards -> servos ->
?mounts? -> machine, with a VFD for the spindle.
Thanks,
Michael Larson