727rebuild/ front pump questions

If you decide to swap in the planetaries from the van, be advised that Mopar changed the shape of the drive splines, somewhere in the late seventies I think. The spline count is the same but the shape is different. It is possible to swap them , but in a few miles the old shaft will nicely machine out the splines in the replacement planetaries, and forward locomotion will completely stop. If this happens at WOT, your revs could go thru the roof. I don't recall what year this changeover occurred, so it's probably in your best interest just to not do it,lol.
I have learned that about the spline change and also i believe a gear pitch change with the planetaries themselves. Which is why im going to keep all of my original output shaft componets together and just swap everything from in front of the output. Tranny lasted years (@25) with a 3500 converter and turbo action rmvb.