what is the torque specs for u-bolts and spring eye bolts for a 63 plymouth b-body Thanks

I think the 1/2" fine thread ubolts/nuts would be the std 45 lbs.

I too would suggest 45 ft lb. This is factory spec at least for '70 with similar U bolts. Too tight will bind it up and make it "pop" on bumps.

Always a good idea to re-check torque after driving a while.

On the spring eye bolt I would suggest looking up the spec for the dia/coarse or fine threads/grade 8 bolt.

FSM

from the FSM :
front pivot nut : 125ftlb.
shackle bolt nut : 30ftlb.
u bolt nut : 45ftlb.
front spring hanger to body bolt : 30ftlb.
rear shock mounting nuts : upper-25ftlb. lower-50ftlb.

Thanks

Where does the pop come from? Do the leaves move relative to each other within the few inch span between the u-bolts?

I do believe there is some movement of the leafs relative to each other. If it is too tight, pressure builds up then it moves/pops. I over torqued my U bolts once and had the pop on bumps. Back them off and correct torque fixed it.