This is what worked flawlessly for me when I was putting an LM7 truck motor with 4L60E into my 69 Chevelle 1 year ago.
Body Bushings Energy Suspension
LS swap plates from LSX innovations.com I mounted my motor in the middle position. Part # ST-11 $44.99
Stock Motor Mounts Energy Suspension from Summit Part # ENS-3-1120R $83.99
Holley 302-2 $349.99
Dirty Dingo small PS Pump Pully $29.99 I think
G Force Crossmember from Summit Part #SUM-770308 $259.97
Flowmaster Headers Part # 814116 $747.48
Flowmaster Header back exhaust system Part #FLW817409 $542.99
My entire build was built around the Holley 302-2 Pan. That was a game changer for the A Body guys. I waited about 5 month for it due to the popularity and demand. I followed toddoky on a few forums explaining the pan and how it was built for us A Body guys. I am looking forward to checking out the Holley Swap Kit when it is unveiled, no doubt in my mind it will be another game changer.
The pics below show how everything ended up clearance wise. The lowest part of my drivetrain is the transmission pan. I lifted the rear of the transmission up until it hit the floor and then set my Energy Suspension mount with shims where the rear of the transmission is approx 1/4 in from the floor. The headers tucked up to the floor with less than 1/4 in clearance and continued thru the G force crossmember with almost the same clearance. I had my driveshaft shortened 1 1/2 in, re-balanced and upgraded the u-joints. I did not check my driveline angles before my first test-drive but there is no vibrations and nothing hits with my setup after almost 800 trouble free miles.
Build Thread http://www.chevelles.com/forums/showthread.php?t=671226&highlight=