Back Spacing question

I've measured the back spacing on the original wheels on my '83 Caprice. It looks to be 4" or maybe 4.125"
I want to put Cragar S/S wheels on it. Original wheels are 7" x 15".
I'm thinking of 7" front and 8" rear.
So, I can put new wheels with a backspacing of 4" or less - correct??
However, seems to me you'd not want much less, especially if I go with wider wheels, as that would shift the center of the wheels toward the outside of the car and would that not be rather hard on wheel bearings?
Can somebody in the know on this tell me if I'll thinking correctly?
Thanks

What do you mean by the back spacing on the original wheels?

What do you mean by the back spacing on the original wheels?
I measured the original wheels that came with the car when it was new (that are still on the car).

Oh I think I know what you're talking about... You can go bigger, and it wouldn't really hurt the bearings, but if you go with a bigger diameter tire, It'll knock off the accuracy of your speedometer a little bit. I'm not sure how big or wide you can go, but an inch or two probably isn't gonna hurt anything.

I just wanted to be certain I have the back spacing issue clear in my head so I don't buy wheels/tires that don't fit.
Since the back spacing on the original wheels is 4" (and that obviously provides adequate clearance to the inside of the wheel well) I could put new wheels on the car with 3.5" backspacing with no problem, but maybe not 4.5" as they might rub somewhere on the inside - right?
All this assumes the tire diameter is no larger than the original tire size recommended by GM.