Last night I took the Cuda out and I could not get the shifter to engage over so I could get the linkage to slide into reverse? Its always been kind of stiff but it would go in. Any one ever experience this issue? I've removed the handle and linkage and I believe its in the mechanism I hope. May need a rebuild and other thoughts?

Sometimes a simple readjustment helps. It's a basically simple mechanism so you should be able to find the issue without too much trouble.

With the linkage rod removed from the Reverse (bottom rear) lever and the two front levers in Neutral, use a Crescent wrench and see if you can engage Reverse. If not, the interlock inside the side cover might be out of adjustment.

A FSM outlines the procedure to adjust the interlock.

All of the above good info, I might add though I had a similar problem with my factory Chrysler 4spd/pistol grip, the culprit was the thin stainless shim slider plate(s) that are between the shifter plates/arms in the shift box mechanism, the one between the reverse plate and the forward shift plate curled up and prevented the shifter from moving/engaging the reverse detent

You need to adjust the reverse interlock by loosening the side cover bolts and tapping the rear end of the plate up until there is only a slight drag going into reverse. The FSM explains the process.

You may have something here:

I played with the linkage adjustments yesterday, no luck so far. All shift movement is smooth but the shift arm will just not move over to the right to allow it to move the reverse rod. When I'm under the car I can move the reverse rod forward and aft by hand with no problems. I will tear into the mechanism tonight and check out those shim plates. Stay tuned

May be a silly question, but I assume you used the "rod" tool to align all 3 lever plates on the mechanism? If they are slightly mis aligned, won't allow the reverse gate.

The simple rod won't work on a '70 shifter, there's no hole for it in the Reverse rod. You need the factory alignment tool, or eyeball it (trial & error).

Thanks for clarifying, John. You are truly the "keeper of the archives"

Well I disassembled the mechanism and cleaned and lubricated all the shift plates, steel shims and internals. It now all works and shifts much smoother. Its an original piece and I probably need to pick up a rebuild kit from Brewers

Works Great. Thanks for all the helpful tips