wheels offsets for 20 x 8.5 and 20 x 10's

Depends on the tire size, section width, and owners preference on look.

Old post by CrazyDave that I think sums up back spacing pretty good
On a stock fender car, the prefered offsets are: Front, 4.75 for 8 inch rim, 5.25 for 9 inch rim, 4.25 for 7 inch rim. Rear, 5.0 for a 9 inch rim, 6 for a 10 inch rim, 6.5 for an 11 inch rim. This is the distance from the mounting surface of the hub to the rear most lip of the rim, NOT THE TIRE BEAD Subtract .25 if your dimentions are to the tire bead.

Thanks for that.
Umm are they std ford bolt pattrn
if I read that correct, they are the opposite to deep dish , is that correct ?

Standard ford 4.5" bolt circle
and yes they are reverse deep dish style if you want to fill out the wheel wells with as much tire as possible