4 spd. pops out of gear.

You will not fix the 2nd gear issue with just a rebuild kit. That might not even just be a "gear" issue, that could be an issue with shaft play. It might also be the adjustment on the shift rods, but it's not unusual for 833's to pop out of second gear on hard deceleration with engine braking. A high compression engine exaggerates that issue too, it will engine brake harder which makes the 2nd gear popping out thing more pronounced.