Four-speed automatic tranny on my 5.7L/355 engine is from an 87 Cam with 5L engine. It was inspected & in good working order when I did my engine switch & takes the torque well, but am wondering whether car can be upgraded to a five speed automatic. Can it be done? What would it take? What would it cost? What are best places to compare prices? Should I just wait till the tranny goes? It has 110,000 miles on it.

Idle thought, but the hard stuff is done & am wondering what's next. (Probably will be decided for me; wheel bearings, I suspect. Car has 156,000 miles & was used as dirt racer by previous owner.)