Which would be more fun, a 904 w/a 3000 stall or a 5 speed?

If you like to actually drive go with the 5spd, if you like to just sit there and steer go with the auto. When it comes down to dollars and cents the auto will probably be the way to go since you already have it. Personally I hate automatics unless its in a racecar.

With a reverse manual valvebody, I should have a it more control than a normal auto. I have never driven a manual valvebody or even a trans with a shift kit before.