I'm searching for a 5-speed overdrive transmission for this truck. The SM 420 Muncie got cooked while towing engineless. Is there any OD 5-speed that will bolt in? Yes, I know - ALWAYS remove the drive shaft . . . It had a 265 and will have a 327, but I'd like to slow the engine down a bit. As I remember it, even in high range about 50 was top speed.