Jeb1865

I have searched, and haven't found something quite unique to what I am asking for. I have a 1991 Pickup DLX 4x4 manual sitting on 31x10.5. I need to replace the tires, and I am going to go with 33x12.5x15s. I am buying new wheels too, because the stock ones ( I think are stock) are just trashed. I am looking at Pro Comp or Trailmaster black steelies. The question I have is for backspacing on the new wheels. I do not have a lift, and hope to squeeze the 33s on without one. I have seen where people have made it work, and from the looks of my truck, it looks like I might be able to, maybe with a little bending. It looks so high, just stock. But I digress, the guys that have squeezed 33s under their trucks without a lift, what backspacing do you suggest for my wheels? I am going to do 8" wide wheels. The options seem to be mainly 3.75 or 4.5. I have no idea about offset either.