What motor mounts are you using?I have had Sanderson BB1s on my '56 since the early 90s. They work with the stock tranny mount frame horns. Exhaust routing is a little tricky, but fairly easy with 2 1/2" pipe. I have Heidt's dropped spindles and springs, and have few issues with ground clearance.
You can see on the passenger side I added heat wrap to the exhaust pipe to help shield a stock (not mini) starter from the heat.
The two driver side pics show that the header more than adequately clears the stock steering box.