as we toured the Great West Truck Show we ran across an ad of this folks, selling any kind of diesel motors and transmissions.
http://www.adelmans.com
Adelman's in Canton OH
8006432001

some listings:
3208 CaT 2500$
3208T 2950$
Detroit 8.2-T 2450$
20 Detroit 8V71-T 1950ea. military surplus
long list, but we never used this people, so buyer beware