/6 sitting up for several years what to do

The '67 and earlier engines will all swap amongst themselves without any modifications except for an automatic crank engine going into a manual application. In that particular swap, you'll have to cut down the pilot bushing or machine the crank hole to accept a stock bushing. The automatic crank has the same hole but it didn't get the final finish job that the manual cranks got so it's a little too small. If you install a '68 and newer engine to a '67 and earlier automatic transmission, you'll need to use the '68 flex plate and get a special bushing to make up the difference between the small convertor button diameter and the larger crank hole or you may end up breaking flex plates. Without the bushing, it's hard to center the convertor and keep it from vibratiing. You can't just swap the convertors because they changed the stator hub the same year. You would have to change most of the front end of the transmission to do it that way. Another way to do it is to have a special convertor built with the features you need on both ends. The bushing is the easiest solution.