b and m megashifter nightmare

My car is about ready to go but I am stuck on the shifter. This shifter came out of a 64 cuda I used to have with small block. My new barracuda is also a small block with a 904. When it was in the 64 it seemed to shift fine. But it was in that car when I bought it. I have it set to where both adjustment points ( swivel nut and cable barrel) are right in the middle of their range. I set shifter in park and pulled tranny shifter arm into park ( towards back of car). Swivel nut came into shifter arm hole nicely, but when I shift the shifter to first it doesn't quite seem to make it, almost but not quite.
The cable doesnt seem to be melted and it travels nicely in the housing. I have the cable installed with about the biggest , smoothest loop I could make. I have the cable housing protected near exhaust with 2000 degree heatshield tubing. Is there a special shifter arm I am supposed to be using? The one on there is just the stock arm. Any other ideas?
Bonus question: why when you click through the gears down below with the shift arm, why is there 7 positions rather than 6, as in PRND21 ?
Thanky, Neal