Have a good friend who has a set of Cup 1 wheels he had on his 928, tried offset calculators online though none give info on if they would fit with spacers or how thick spacers should be if could possibly fit.

My car is a 1986 944 Turbo with 16" OEM Fuchs wheels

His wheels are
17 x 7.5 ET 52
and
17 x 9 ET 47

Anyone (and flame suit on) confirm if will work on my car and if so what spacer thickness? Hoping they will as he only wants $500 for the set

 

You're definitely going to need spacers since you're putting late offset wheels on an early offset car. I am running a somewhat similar setup on my '86 951, and I had to run *I think* 25mm rear and 15mm front spacers (both hubcentric). It's been a very long time since I bought the spacers, so I'm not 100% sure on those numbers. I'll let one of the wheel gurus chime in with their expertise to give you specific spacer data.
I'm curious why you want to get rid of the Fuchs? Is it the increase from 16" to 17"? I've often thought that I would love to switch mine back to Fuchs (probably LR 17") so that I could get rid of the spacers- and Fuchs just look SO good. That being said my current wheels do look really good and drive great, so I doubt if I'll be changing anytime soon.

 

With those offsets, they will be replica Cup 1s...and much heavier than the factory Fuchs. As a result of the additional unsprung weight, vehicle handling [accelerating, braking, damping, steering] will suffer.

While they can be made to fit your car, there is no one size fits all, as each chassis is slightly different. How aggressive of a fitment are you looking for?

In this case, short answer for spacers...30 mm front, 25 mm rear. With a resulting effective offset of 22 mm, front and rear, those size spacers will get you pretty close to a factory offset/backspacing.