I just bought a complete 74 C10 with 454 and a new TH400 (and a buncha other new parts) for $550.
The 454 has a rod knock. That's ok. I'm buyin it for the suspension and steering to transplant into my 64. The 454 is just a bonus. And I've got guys askin me for parts off it already. I may make enough in partin it out to come way with the suspension, steering, rear end motor and trans...and still get my $550 back.
There are plenty of deals out there. I found this one in the local thrifty ads. Keep your eyes open and one will pop up.