15x8 with 4-1/2 backspacing fits with no rubbing. You might fit a 15x9 with 4-3/4 BS but it would be real close to the inner fender. 255/60-15 will fit either wheel. Maybe you can get a 275 in there, but it would be real close on both sides. 255 is more than enough tire anyway.
It looks like there's all kinds of clearance there, but the outer wheelhouse slopes a bit near the lip, so if you want to be safe, go 15x8 and 255/60.
Edited by Old_Guy_Stu (07/31/21 10:18 PM)
1988 CVLX Formal Roof (Love Boat) POTM July 2019 & Aug 2020, 56K
E-code lights w/ relays, LEDs w/ switchbacks, 15x8 Ansen slots w/ 255/60 BFG's, Kenwood stereo, various hacks.