budget 4 speed swap?
Manual valve bodies get old after awhile. In fact you already have one on your gear selector. Works just the same, with out the full time harsh shift. Your swap isn't gonna happen under $1000 all said and done, more like $1500. The need-a's will stack up quick. Just being realistic.
Rebuild the 904 add a TF-1 or 2, and have fun. Be careful adding stall, read up on what it actually means.