-if i need to buy one:
out of a truck that you didn't see run at time of removal: $300
core:$300
out of a truck you saw run: $500-900
complete rebuild with papers and clean: $2500
rebuild with better parts and papers: $3000
-if i'm trying to sell one, half everything. or be ready to sit on it for a year. i suck at selling used parts.
Thats the answer I'd gow with.
How hard is it to swap a C6 to a E40D?
Hard isn't the word I would use. Expensive is more accurate. Its mostly a bolt on deal if you have all the parts but between the cost of a transmission controller and trying to be sure your E4OD will be as reliable as the C6 it replaced - it won't be cheap. If you don't care about reliability and just pull all the guts out of a parts truck, well budget for a parts truck.
If you do care about long term reliability, budget for a minimum $2500 to get a decen't updated transmission with known history in there. I have over $2000 in my swap (rebuilt it myself however) but its paid for itself in a couple years due to the amount of miles I run on the highway.
The 3.08s broke even in a couple months though