Go for it. I was trying to get a friend to do the same thing. There should be plenty of spare parts available, and not only will they be cheap, but go-fast parts for the 302 V8 shouldn't cost much either.
With the low-end torque(especially after some power mods), you might not need a manual. Try drifting it using manual shift between 1st and 2nd before you look into a swap. There's a guy in my area who does very well drifting an El Camino this way(won Drift Showoff).