Why does the suspension look like i drove over a rock?

I went from 28X10.5 MT to 28.5X10.5 Pheonix they have much stiffer sidewalls. The bounce / spin at hit is the tire being hit too hard and crushing the sidewall. Leafsprung Mopars have a very short instant center (spring eye) which causes this. Stiffer sidewall slicks, tubes if you're not running them, more air, GOOD double adjustable shocks, taller gears, wider rims, will help. Unfortunately if the track is crap its gonna spin.
You might also try less RPM on the start line. It looks like you've killed the chassis reaction coming up too high on the converter.