radar, I wouldn't worry too much about the motor/trans being 1.75" off center line with the rear axle center line. You just need to be sure the trans center line is parallel with the center line of the pinion shaft in the rear end, and the final angle is still in the operating angle of the U-joints, which I think are 30 degrees or less. It doesn't matter which direction that U joint angle is in.
A 1/2" clearance between the oil pan and the frame using good spool mounts should be good. The motor torque tends to lift the left side of the motor (unless your doing burnouts in reverse...)

My 54 wasn't a pretty truck before I started on it. I had to buy the front sheet metal from Texas to get something good enough to work with, the original metal was bent up rusty stuff. Unfortunately, nearly all my pictures went with the truck, which I sold about 15 years ago. Gene