shifting problems

The kickdown rod missing is the problem. BTW: Mopars don't use a modulator valve. That's GM stuff. Get a kickdown on it or you'll burn up the transmission very fast. The kickdown linkage not only provides kickdown and proper shift timing but it regulates clutch pack pressure.

IMO it's in your best interest to not even use the stock kickdown linkage as it is somewhat temperamental and hard to find in good used condition. I have a Lokar cable setup on mine. Much cleaner setup and easy to adjust. Bouchillon also makes a real nice kickdown cable setup. I doubt either will cost you much more (if any) that a original setup in good shape and they look much better. Since you are familiar with a modulator valve it sounds like you know GM's. That being said think of it like the 350 Turbo's kickdown cable setup.