1968 Barracuda back space question

Sorry to add to the deep well of wheel and tire threads. I searched, but did not find an answer for my specifics.

68 Barracuda 8 3/4 with small bolt pattern
I have an old set of slotted 14" rims I want to put on, I measured 3" backspacing.

Had 255 60 14 tires, but they are old and near shot.
I am looking for 275 or 265

Aside from even being able to find such a tire; is the 3" back spacing of concern?

I could try to find vintage 15" slots but that is going to cost $$$ and small bolt pattern will make it even harder. If the backspacing is not an issue, I will go ahead and order the tires.