904 Lockup Transmission Adjustment Help needed

Hi, I have a 904 lockup out of a 1979 grand fury had a shift kit installed and had the converter peeled open to stall at 2200 rpm, kept lockup, and I have it behind my small block in an A Body. And thats it, no other special work done. The problem I'm having is it will shift 1st, 2nd then automatically into 3rd lockup. Adjusting the kick down doesnt seem to help much, but it always wants to shift from 2nd right into 3rd lockup at 30 mph with light throttle, or any speed for that matter and with 2.76 gears and 26.5" tires, that makes the car chug. I want to adjust it so it goes into lockup at a higher speed, maybe at like 45 if possible since it has a small cam. How can I adjust when it locks up?? Id like it to shift it a little later too, but I guess I can put a little stop in front of the kickdown so it doesn't come all the way back and shift too early at light throttle... Please advise!