Gregg, it is possible that the rebuilt starter you got was defective from the
start (these things happen).  I have had some bad experiences with anything
but Bosch rebuilt starters (have had infant mortality with the others and I
hate doing work over).
The other thing that could be causing your problem is your positive cable
from the battery to the starter.  This is a long cable and already has a
decent voltage drop before it gets to the starter.  So if the cable is
corroded at all this will increase the resistance and basically when you get
to the starter you are not getting enough juice to crank it over.
I can send you a good, used cable for $20 or I have some new ones coming that
I could help you with if you need one.

Hope this helps,
Ken Wilford
http://www.vanagain.com
John 3:16
Office (856)-765-1583
Shop (856)-327-0027
Fax   (856)-327-2242