P rated is essentially the same as a 4 ply, unless it's XL rated, which is a 5 ply rating. LT tires are rated for heavier use, thye generally start at 6 ply, and are built for extended heavy load usage. For what you're loking at, a P rated will probably do fine.
I agree with the Coker issue. Nothing against Coker tire at all, but they really are more geared towards the restoration/hot rod crowd. What we're dealing with here is a completely different deal.
