Is it possible to change a 95 SL320 to a Manual Transmission..?

anything is possible with money.But you can get more hp,to drive that trans. turbobandit.com

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

The same year 280SL uses the M104 and was available with a 5-spd, 717.444.
I would check the EPC for the part #'s of the clutch pedal pieces you will need and see if they are still available from Benz. I use OE discount parts to check.
Otherwise could be a long and frustrating experience.

Possible but not a money saver over rebuilding the auto trans. 95 / 96 is the last year of the analog engine computer. 95 is the last year for the hydraulic shift trans ( 96 - 97 got the 722.6 electronic shift that is more integrated into the electrical system. )

The 90 300SL came with a very rare 5 speed but it is reported that it didn't suit the car very well.

You will need:

Brake / clutch pedal assembly, one from a W201 / 190, or another car I can't think of.

Flywheel with 3 wings to run the crankshaft sensor. W201 / 190 with a 2.6 inline 6 is a candidate as well as a car with a 3.0 M103 .

Clutch / trans not sure what to use here. Probably the 190 again or try for a R170 / SLK230 as this is the same bell housing pattern.

Shifter, use for trans selected above.

Longer drive shaft, make a sleeve or take 2 and cut.

At some point I'll be putting together a R129 SL track day car and eventually plan on a manual trans but that is a while from now.