I have bottomed out before with my Big Block but never with my small block so I am assuming you are running a big block engine. When I converted to the FE engine I got some new frame mounts that are almost a full inch shorter than the small block mounts. I am running 450 # front coil over springs which I have adjusted all the way up (two reasons: 1. Clearance 2. Handling). Also, I am running a Lakewood steel bell housing and it sits a full inch lower than my
oil pan. I drew a line along the lower 1" lip of my bell housing and cut it off. You can still mount your inspection plate and add an inch of clearance too.
Also, I have a friend with a B&B that literally pulled the bellhousing off the rear of his engine when he went over a rail road crossing too fast and caught his bell housing. Now he is using heli coils to hold his bell housing onto his block.
Clois