I moved the springs with the 3/4" offset kit, this puts the springs just inboard of the inner face of the wheel well, so the wheelhouse becomes the limiting dimension. IIRC the tub is just over 14 inches on my 68 Barracuda.If you are a streeter you can run as little as 1/2" tire clearance (less with nearly flat, de-arched springs) and not worry about rubbing. So that allows a 13" section. 13inches converts to 330mm.
I can run 325s with enough clearance for straightlining. With a bit of beating the inners in key areas, I am able to corner fairly aggressively before it rubs on the inner.
I do run 295s without worries. They have never rubbed.
I had some vintage 10" al. kidney slots(Ansen Type), that I liked very much. They have a 4.5 inch backspace. If you check catalogs, you will find most 15x10" al wheels come on 4.5bs. So I had the rear narrowed to center the wheels.I figured if I wanted to change wheels at a later date, I was all set.
I cannot recall what I narrowed it to.But I seem to recall it was narrowed as far as possible as the perches were right there. So for me,4.5bs is the only bs that will fit the 325s.The 295s have just over 1" clearance on the outside and a tad less on the inside. So I could run between 4 and 5 inches of bs, with the 295s
The best advice I can offer is to buy the 295s which I know fit in there, and the 10" wheels of your choice with a backspace in the 4.0 to 5.0 range. Then pull the diff out, and roll those babies in there. Center them up, drop the body down to simulate a speed-bump, and recenter.If you get lucky, you might not have to relocate the springs with the offset kit, but if they are in the way, drop them out too.Once they are in and centered, measure between the mounting faces and send your diff out for narrowing, and possibly perch moving. This is not that expensive. If you already have the wheels you like, then it costs less than a lot of new wheels.The real cost is time, or rather downtime.
