This past spring I did the T5 for T-50 swap in my 77 Starfire. I used a T5 out of an 86 Firebird V6 and had the rebuild shop change the gear ratios for me.
The T5 is roughly the same size as a T-50, but the shifter is a little further back - see image attached. The F car T5 is mounted at an angle so this complicates things somewhat.
I fabricated a torque arm mounting plate from heavy guage steel, and bolted it to the 3 holes in the T5 and the stock torque arm.
I cut the transmission mounting pad off of the tranny and instead bolt the tranny to the stock T-50 mount with a big U-bolt from a pickup truck rear spring kit. (Welding a new pad would be so much better)
I used a T5 Camaro Hurst shifter 391-5032, reversed the shift arm, then added a shortened 528-7236 chrome stick, and white 5 speed ball 163-0008. The T-50 shifter boot and trim ring fit fine.
I used the stock tranny cross member and mount, stock shifter boot and trim ring, an 86 Firebird clutch disc (actually used one from a Quad4 5 speed tranny - they are the same) and the T5 back up switch connector.
Only down side I have noticed so far is that you cannot downshift at high rpms as the synchros will not let you. Perhaps a world class T5 would be better, but then they have electric speedometer outputs.
Let me know if I missed anything.
Jeff