budget 4 speed swap?

My 2nd gear is gone in my 904. As a teenager, I think having a manual would be awesome even if I do lose a little time at the track. What would be the cheapest way to swap in a 4 speed? donor vehicles and what parts from them? new drive shaft?
Its a 73 duster 318 magnum, 904 auto, 8 1/4 rear-end. My other option is to rebuild the 904 with a shift kit and higher stall. any tips on that would be awesome too! thanks!