Motor Mount Location

[1947chevypanel]

I am doing a 47 chevy panel build. I have installed a TCI Mustang II, power rack, and have not yet removed the factory firewall. I haven't decided yet if I want to do a new firewall, but I am not opposed to it. I am having trouble placing the motor mounts in the correct location. I see in some of your pics, they are placed 1-2 inches behind the crossmember, some are farther back. The mounts are the TCI triangle type. Maybe some of you have some good pics to give me an idea of where to start. I'm using the standard chevy 350. Thanks all.