15x8 w/3.75" backspace question

He told you what the offset is, indirectly, but as usual it has to be calculated, as opposed to BACKSPACE, which is simple, and measurable. Exactly why I don't like that offset bullshit, besides the fact I can't be bothered to figure out which direction is + and which is minus.
15x8, which is really 15x9, with 3.75 backspace is 3/4" offset, or 18 or so mm, and I don't know or care + or-. The b.s. tells me that.
Since I don't know what year barracuda he is talking about.... 64-66 MIGHT fit, with the SMALLEST appropriate tire for the rim width. (Assuming no wheel adapters. If it has wheel pattern adapters,, there is NO way that wheel fits!) A 67-69 should be easier, considering the more open ww opening, IF it doesn't have too much tire on it.
As always, the wheel with the correct b.s. will fit the best (4.5 bs).