Reverse Occasional Grinding Question

Ok guys heres the issue. Every once in a while my tranny grinds going into reverse. The only way i can get it to go in is to go back into gear move a little, then go into R.

Now this doesnt do it all the time. It almost always does it if ive been driving forward and then go to back into a space, like at a show or back into my driveway. It seems like the gears are still spinning at a constant speed. If ive been parked, I can start it and go from 1st right to R no problems.

This part sounds weird, but it seems like (for example), say i leave my house to go to a show. If i get on it, not real hard just a good run through the gears, during that drive, it will be more likely to grind when i try to back into a spot at the show.

-Ive adjusted the rods, no change.
-Adjusted the clutch, no change.
-Fluid change, no difference.

Heres my process of normally going into R. Stop, go from 1st to N for a sec, then go to R. Sometimes it goes with no problem, other times it grinds.

Heres what ive noted about when it does it.
-I can stop, go out of 1st to N, wait for a sec then -go to R. Still grinds.
-I can stop go directly from 1st to R, still does it.
-I can stop go from 1st to any other gear back to N for a few then try R, still does it.
-I can stop, go from 1st to N, let clutch out for a sec, clutch back in, then try R and still does it.

Specs: 71 duster, 360, Brewers built 4spd (P.O. Installed) less then 3k miles on it, hays clutch, hurst comp shifter with pistol grip. Previously had hursts short shifter, the one thats like 12" long if that, and i cant remember if it ever did it with that shifter or if it just started after the Pistol grip install. But I dont see why a diff shift handle would make a diff.

Whats everyones opinions? I tried to put as much info as i could think of and everything I have tried while experimenting with it. I really want to figure this out. Its more embarrasing than anything when it does it. Makes it look like I cant drive a manual.