clamshell mount placement

[sammywells]

Working on a 68 1/2 ton with 350 and Hei and a 700r4. Using the later clamshell mount. Brackets are from a c20. My question is where do i mount the brackets to the frame so the i have enough clearance with the hei and firewall. There are different holes in the frame but not sure which ones to use. Right now I just have a rolling chassis and want to mount the engine and want to make sure the engine doesn't hit the firewall when i put cab on. Transmission mount is already loose and can be moved.