76 Stingray. Having trouble getting the motor to sit right!

[Cat Fuzz]

This is a project for the guy I'm working for. I started in the middle of it. We have a fresh 350 we're putting in but we can't get it to sit properly on the mounts. I'm thinking the frame is twisted or something or are there actually different left and right motor mounts? Every parts store swears they are the same.

When we bolt down the left side, the right side is too low, the mount is rotated a couple degrees of where it seems it should be and the engine is obviously lower on the right. Any suggestions?