https://www.jegs.com/i/American-Raci...76540/10002/-1
AMERICAN RACING AR500 TWO-PIECE POLISHED 15 x 7 5x4.5 0 4.00
This would be for my 1967 Cutlass Supreme Convertible looking to do 15" and buy the appropriate tires later.

Also would anyone have experience with these, bad/good opinions?

 

The wheel you are talking about here will not fit your car. It says 4.5" bolt pattern and your car uses 4.75" bolt pattern.
Nice looking wheels!

 

Wow, those are high dollar. AR is a good quality wheel. However, the one you chose is the wrong lug pattern. The link below is the correct wheel. What tires are you planning on running?
American Racing VN500576137: AMERICAN RACING AR500 TWO-PIECE POLISHED 15 x 7 5X4.75 -6 3.76 - JEGS High Performance

 

They're polished aluminum. The plated steel ones from Coker are half that price.

 

Whoa, don't know why they're showing $400+ there. Normally they are $120-$160ish!

 

As for tires, I know things right now seem somewhat limited as far as variety to choose from. Hoping for a 15" 225/235/245, visually looking for a white wall ideally, or alternatively black wall.

Oh also backspacing- isn't that normally 4.5", but I suppose maybe that's dependant on the wheel design?

 

BS is dependent on wheel width and or where you want the tire to sit inside the wheel well. Some wheels have different available BS for the same width.

 

I just popped on AR's website and the part they suggest is:
Link to AR's suggestion on Jegs
It looks like (besides the finish being different) the difference they list is a BS of 4" vs what you had linked @ 3.75" BS.
So am I right in suggesting both may fit, just be positioned slightly differently in the wheel well?

 

Backspace depends on both wheel width and offset. The dimension you really care about is offset, which should be as close to zero as possible for these RWD cars. Unfortunately most wheel vendors list the backspace measurement because it is easy to measure, but it's less useful information.