Are you sure that your shifter is adjusted correctly in all gears?
If not do that first before fixing something that may not be broken
I've seen this on more than one Mopar, A,B and E bodies
The shift rods and shift levers get worn and won't let the tranny engage the gears properly and completely
To check it have someone shift it into each gear one at a time and then remove the shift rod from the tranny shift lever and see if you can move it forward more into gear, make sure and watch the lever when you remove the rods to see if it moves on its own
Good luck, let us know what you find
