hi! i have not raced in 15+ years

have been jr racing with my son for 5 years, so i have a few questions
i found a stock suspension 1967 camaro with a fiberglass front cap,that i am building for my son (and i get to get in till he is old enough

), trying to start with suspension and work my way up, it will be set up with a
12 &1/2 to 1- 355 small block , th350, 8inch converter( the 1st owner said 5300 stall

), 488 gear,
looking to see what size rear tire should i run (30x9?)
i really don't want his 1st car to leave as high as you guys

,so can i use caltracs (or something similar) to keep it down and still be consistant
thanks for any imput at all (good or bad)