Using the 55-62 car bellhousing does give you clutch issues due to the different angle of the fork.
I know cutting out the center section is necessary for the T5, but not sure on the others, I would think it would be necessary.
If you do make the bellhousing sidemounts work, then no support under the tranny is necessary. Otherwise, a tranny support can be made as part of the crossmember section that you cut out. Make it boltable though, otherwise you can't get the tranny back out...
Your stock springs will work fine, I believe the 55-57 perches are in the right location, just measure them for yourself and see. If not, cut them off and move them. Install the rearend, etc... before rewelding the perches so you can make sure you get the proper pinion angle. Also note that the rearend isn't centered over the spring bolt, but is about 1 1/2" farther back, so drill another set of holes in the perches for proper rearend location.
Speedway sells a cheap set of U-bolts and lower mounting plates with shock mount if you need them.
The 55-57 driveshaft should work, worst case, you would need to have the length changed. There are places that will shorten or even make from scratch a driveshaft. Check your local phonebook.
The easiest way to go open driveline would be to go with an S10 T5 and an adapter plate from Buffalo. Then you can keep the 216 bellhousing, But it only works with the S10 T5 with the longer input shaft. It would also require changing the clutch disc, and the output splines are different, so the 55 driveshaft will not work as is.
