I waas able to buy a Lakewood bellhousing that matched up my FE to the RG transmission, the 5-speed with 5th being 1:1. They may have one for a small block.
The shifter I use on the RG, a Hurst I think, isn't the speediest, but fine for the street.
I seem to remember the RG is supposed to handle up to 600 Hp, however my quick check of their website only mentions 600 ft-lbs of torque.
If you order one, pay careful attn as you have 3 options for 1sr gear ratios.
A selection of the 5-speeds is here (click on one and it brings up the specs, dimensions, etc.....note there are Ford units):
http://www.richmondgear.com/01fivespeed.html
The info for the OD unit is here:
http://www.richmondgear.com/07pdfs/RG22.pdf