To the OP, trucks are selling for a lot of money right now. I’d ditch the 6 speed Ram 2500 in a hot minute. Get top dollar and be done. 64rfe is not a very good trans, not unlike basically every other in house Chrysler trans since the 80s, lol.
Even the ones that work, are clunky, poorly executed examples of automatic transmissions.
JMO
I’m a Mopar guy and wouldn’t recommend any 46/47/48/545/64/68 re transmission without a word of caution backing it up.
I have a 68rfe behind a tuned diesel right now and while it is solid or appears to be, it’s still an ill shifting poor example and it’s actually tuned to help some of those issues !