Converter and gear swap.

I did a quick check at Randy's Ring and Pinion.
For what it's worth, their calculator says that your engine rpm at 60 MPH will be as follows:

with the 4:56 gear and a 26 inch tire: 3630

with the 4:56 gear and a 28 inch tire: 3371

with the 3:55 gear and a 26 inch tire: 2820 (which is the same as my Challenger with the same tire size and gear ratio).

When you change your engine over after it's finished, all this could be thrown out, including what stall your new engine combo will need. New engine, different specs for your converter. Don't blow your money or waste your time on a converter until you've got everything together.