Ok, my first thought is that if you have 7” wide rims on the front and still want a 3” (!) spacer, then those wheels have a totally wrong offset for the application. If they were dished deeper (more offset outward) you would need much less of an adapter. AT MOST you should be looking at 1-1/4” spacer on a flared car in the front.
Same for the rear. If those rims really are 10” wide there should be a lot of offset outward and less offset inboard because of the interference with the suspension spring plates. If the offset dishing is done the way it should be, there should be no need for spacers either front or rear on that car - somebody simply spec’d the wrong wheels for the car.
Because of the torque forces on the wheel bearings when moving the wheel centerline around when using spacers, I would be reticent to run spacers larger than 2” (and that’s a lot, too). 1-1/2” would be a max for the VW-style wheel bearings.
@Troy Sloan might be able to provide more insight, I’m sure.