nf65fleetside used them , here is a link to his build:
http://67-72chevytrucks.com/vboard/s...d.php?t=279769
also I had pm'ed him asking about the same thing, here is the message he sent me:
I used the tubular v8 mounts the Truck/Car shop (same as all the truck parts stores though) Motor went in the same location as the sbc, not moving forward or anything like most suggest. Only reason for moving forward would be to have clearance if you run tall valve covers...the motor clears the firewall but with tall valve covers you will hit the master cylinder and or booster....as for trans cross member, i was running a 350TH already so I just opted for a new cross member from Truck/Car shop as well but could have left the original....drive shaft was ok, didnt need to adjust length due to no movement of motor and trans.
Going to a BBC is very simple, even down to running headers with it as well. Just find a set that is for a 67' to early 80's truck and your in business. I heard all of these horror stories of fabrication but once I got under the hood I laughed at all the guys making it way harder for themselves. Oh and theres no issues with weight too...I drove with cut coils in the front with mine and found no understeering issues or even plowing when braking. Any other questions on it drop me a line.