check this site for the wide variety of HURST levers that will mount to the TREMAC "shifter" with just a small bit of machining.
check this site for all of the information you could ever want on the TREMAC 3550 5 speed overdrive.
I understand there are other companies that are now selling this transmission. There is also supposed to be a new model coming out with a different first gear ratio.
I have a TREMAC 3550 in my '57 150 sedan and love it. The 3.27 first gear and the 32% overdrive is the best of both worlds. The shifter is nothing more than a lever and a mounting plate, much like a VW or Mustang T5. With a very little machining of the stub, you can match the bolt pattern of any HURST lever that is sold.
The shifter will be in the center of the transmission hump, not over to the drivers side. There is no exposed shift linkage to deal with. You can order 5.0 heavy duty shifters from FORTES, purchase a shifter from HURST, or just determine what HURST lever you can use in your application and order just the lever.
There are three mounting positions in the TREMAC 3550 which are determined by how long your arms are and what type of seat you will use. In my application, the shifter is about 6-8" in front of the bench seat with the seat all of the way rearward.