Wheel backspacing question

[Local Hero]

I'm still working on my sister's 86 MCSs.

Had a few setbacks. And am finally turning the corner on getting it back together again.

She's having difficulty deciding what she wants to do about wheels. She's leaning towards upgrading from the stock 15x7 to 17x8.

For those who have done this, did you go with 4.5" backspacing. I measured the stock wheels to have 3.75" bs. Im trying to talk her into the repro stock wheels that I'm seeing with a 4.25" bs. The American Racing VR501s that she's leaning towards come in 4.5".

I'm thinking the extra quarter inch isn't something to worry about. But since I have you guys to ask, here I am. Oh and the car is slightly lowered with a coil cut out of each corner spring.

 

[Ribbedroof]

4.5" backspace will limit tire width to 245 or 255 to avoid rubbing. Wider will require longer studs/spacers to avoid contact with the frame rail.

This is my experience with Malibus, others may vary. I don't own a Monte, but I presume the frame width to be common across all carlines.

My Malibu coupe is currently set up with 4.5"BS Weld Prostars, 275/60 tires, 1/2" spacers and 2.125" long studs. If it cools off anytime soon, I'll be giving it an enthusiastic test drive to verify clearance. Honestly, if i had the chance again, I'd have stuck with 255s, but they were 14 years old and the 275s were free, so.......

I did run some Eagle alloys a while back that were 4.5"BS with 245/45-17s all around with no issues on one of the wagons. They were tight on the rear, but didn't rub.

 

[Kamloops cutlass]

My cutlass has 17x8 4” bs in rear , with 275 50 17 rubber perfectly centred about 3/8” from frame and I had to trim my fender lip for clearance
When I had 255 series on rear there were zero runs or issues
Fronts are 245 45 17 on 17x8 w 4 3/4 backspace minor rub at full lock on frame at rear of tire
Hope this helps