it has been a minute or two since I drove one, but the one I did was also a bit tough to shift. It was a 4 speed, super commando 383. My friend who owned it said that was "normal". I can't remember what transmission it was, I just know it was 4 speeds with reverse. Maybe A833?
Had same issues with several T56's over the years. The OEM's put lockout on the T56's so you couldn't get to reverse while trying to get to 5th. Most of us that put T56's in anything didn't use (or want) the lockout, but yet after driving the first one, I realized real quick that I had better figure out how to make it work. 5th and R are VERY close. Typically you can't get it into R at any appreciable speed but if you were power shifting, it can happen.
T5's had a non-synchronized reverse so half the time getting into reverse meant a nasty grind. Easy way around it, before going to R, go to 4th (sitting still). Goes right into R every single time without any grinding at all.
You get used to shifting the 4 speed, it don't take long to figure out where 3 and R are at. IIRC back in the day when people drag raced the A833's more, they had a special shifter that had a locked out R, had to move a lever to get it into R. Apples to Oranges here but my car is a Liberty and the inline shifter there is no possible way to get it into R unless you work at it--the way it outta be.