Want to know widest 15 " tire and wheel size and backspacing to fill rear wheel well without rubbing

[Hollandshand]

1969 Barracuda. Widest and tallest 15 Inch tire size and wheel backspacing to fill wheel well without rubbing?

 

[SGBARRACUDA]

15 x 8 Pro Star with 4.5" back spacing and Nitto 275x60x15 555R drag radial is the most I could get under my 68 Barracuda. Stock spring location with SS springs and untouched wheel wells.

 

[69FBCuda]

15" Prostar Rear 255/65/15 - 10x28 4.5" Lug pattern 4.5" Backspace. 69 Barracuda Fastback, Stock spring location, stock fenderwells

 

[AJ/FormS]

325/50-15 on a 10 inch rim. Very tricky.Stock tub.Stock 4.5bs. Stock nothing else. 68 Barracuda

 

[Dave Dume]

Need help with 74 Dart Swinger rear wheels with new 440 RB transplant.
Currently stock 14" rims. I need a 15" rim with some backspace.
I do not know a lot about those, The rear wheel wells are stock, no tubs.

Then I will need a tire size for the rims. This Dart has the C body 4.5 spacing 14" rims.
I might fit a 60 series wheel onto the 14" rim. But I think that would defeat the purpose of hooking up with 390 HP.
some CLUB member has done this already. I would be grateful to have the correct sizes.
Thanks,
DDume in VA