727 Shift question?

I have a 727 w/a 2200 MP stall running into 4:10 gears. Trans was rebuilt (less than 50 miles) by a local guy . Non mopar guy, but an old school racer, on the bench rebuild, installed an old, NIB, B and M 3 stage kit ,set to street-strip (the mid set between towing and full out) The tranny was done before (had about 700 miles on it) but sat for over 12 years. I wanted it gone through because the bands will soak fluid, ect. Tranny looked real good, he put in a Kevlar front band. Running a Lokar kickdown. My question is; the car runs, shifts, drives, and is whoop *** , IF, I leave it in Drive. If I try to shift manually (factory floor shifter, 1966), she hangs up (or acts like its falling flat) when I try to jam 2nd. I know a manual valve body will probably fix this, but what gives? I have had 318 column shift cars (and trucks! ) act better when putting on the full effect. Motors a built 340 , sorry for the long post, just trying to give all the info and wondering.....??????????