Would these fit my stock 66Lark?

"Old school" Crager SS Chevy 5 on 4&3/4 with BF Goodrich 225/70SR15.
I'm trying to learn how all this fits together, so please pardon my ignorance.
If y'all know any good threads that'd help explain it through my thick skull, that'd be great.
How can I add a screenshot from my phone?

 

Ttt

 

What is the back spacing? The tire size and bolt pattern is ok I think. Keep back spacing 5" or less and you should be ok.

 

Are these used or are you buying new?
The 225's aren't real wide so wheel offset/backspace isn't critical. If you were trying to fit 255's or 275's it needs to be right to keep tires from rubbing.
The ideal backspace or offset will center the tire in the wheelwell. ...For a 66-7 Skylark, that's about 5" for a 7 inch wheel or 5.5" for a 8 inch wheel.
The common 15x7 Buick rally wheel has 4-3/8" backspace. It'll position the tire a bit to the outside, not perfectly centered. Should be okay for a 245 or maybe a 255.

Here's the Cragar page for the classic 08/61 series:
https://www.cragarwheel.com/wheels/wheelsdetails/series-0861-ss-super-sport

For their 15x 7 wheel, backspace is listed as 4-1/8". That's fine for a 225 tire, but not for a 275 tire.
Cragar also has a '15x7 rev' wheel, called a 'reverse'. Those won't work on a 64-67 as it will move the tire too far out and into the outside fender lip.

 

They're used. How do I tell (ask seller) if they're reversed or not? Would there be a stamp?

 

You can measure the backspace. Put a straightedge across the edge of the rim and measure to the wheel mounting surface. It they're the wheels I mentioned above, it'll be 4-1/8".
You can measure the 'front space' (not a real term, I made it up) the same way.... straight edge across the front and measure to the wheel mounting surface. The 7" wheel would be 3-7/8".
Note if you add the 'front' to the 'back' figure, you end up with 8" for a 7" wheel. Backspace includes the 1/2" or so of the two wheel lips.
The wheel will be 7" between the tire bead mounting surface, but it's 8" wide if you include the wheel lip!

Another method to spec backspace is the 'offset'.
This is the amount the tire is offset from the wheel centerline.
In the above example, take the full width of the wheel (8"), divide by 2 (=4") and the offset is the difference between that number and the back space, so 4-1/8"- 4" = 1/8" backspace. Note Cragar shows the offset in mm. 1/8" = 3.175mm, they round it off to 3mm.

 

Great info. That makes a lot of sense. Thank you.