Front wheel offset

For the least amount of highway wandering due to scrub radius interference, you need to keep the scrub the same or very similar to what the front end was designed around.
This means that if your tires are the same installed height, then the offset needs to be the same as stock. If your wheel assemblies are taller,you can move it outboard. Your 215 calculates out to 25.5 tall. This is about 1 inch taller than factory 14s.I have found on my 68 FormulaS, that running as little as 1/2 inch off the target shows up in the steering wheel as wander at highway speeds.
So a 7 inch wheel has about an 8 inch overall width. A 4 inch backspace would thus be a Zero offset wheel. To move the wheel outboard to play nice with the scrub radius, I suppose about .25 less backspace might be a good target. That then gives you a range of 3.5 to 4.0; with a 3.75 as the target.
Of course with your chosen tire width, this might not be a big issue. A wide footprint is more sensitive, as is a sticky compound.
If it were mine, I suppose I'd throw them on with the 4 inch BS, and if it wanders I could put 1/4 " spacers on and see if that helps. But if your tires get into the fenders, IDK. My head hurts. Too many what-ifs.