Barn Find!!!! Well not really......

I would put a mild 440 in it with a 727 for the sake of simplicity, but if I was really going for it I would put a 4 speed. Clean it well and polish what you can of the original paint, new carpet, redo the front seats, put a repro R/T hood on it and paint it flat black with rattle cans, add the rear R/T valance to be able to put the R/T dual exhaust and tips on it. Rebuild the front suspension, steering, and all the brakes and drive the snot out of it. A vintage air A/C would also be on my list so I could drive it comfortably any time of the year.