I would suggest the bias ply tire. I couldn't get a set of M/T 325R50-15 radials to hook either. Put on a set of 28x13.5x15 M/T ET streets and went 10.90s from dismal 12.00s at 129mph, no other changes. Radials don't seem to recover from the violent hit a clutch car has. You might get the radials to work with an adjustable clutch but I think your tuning window will be very narrow and wear will be high. My 2 cents...
Seems to be the normal thing with a stick car.. just cant
take the shock on the hit.. thats why the bias work better..
on the street you might want the radials
