You can use a T5 5spd from a 4th generation Camaro with the 3800, but it would honestly be cheaper and easier to find a complete engine/trans setup from a Camaro. You would need a 3800 Camaro flywheel and clutch setup (there were no transverse 90 degree manual cars). Likewise, there are small differences in the lower mounting (things like the starter, I believe) that make it much easier to work with the RWD block. Also, the intake would be facing towards the centre of the car, which, depending on how you mount your engine, may not fit perfectly.