cheeta reverse pattern 2nd to 3rd problem

When I shift from 2nd to 3rd the rpms go up before it hits third. Trans does not slip it hits third firm just has a nuetral before it hits. It is an older valve body without low and reverse apply. Also it does not have a accumulator prop installed after removing spring. Does anyone know what could be wrong. Trans was built with a forward manual and was never installed. I bought it installed the reverse valvebody and a 5500 stall. I am shifting it at 7800 and it bounces off the rev limit which I have set at 8000. No matter where I shift at it jumps 200 on the 2nd to third shift. Kickdown band is at 2 turns.Could it be a line pressure problem. If its in third rolling about 50 mph on the street it will break the tires loose as it starts to hit peak torque. There 29 14.5 hoosiers with 456's so the trans does not slip when its engaged. Just on the shift. Anyone have any clues.