Will 15" rims with 3.5 backspacing fit my 69 Baracuda?

Santa brought me 15x8 Ralley wheels with 4.5" back spacing. I mocked them up on my 68 Barracuda yesterday. The rims are 9" wide outside lip to outside lip. They have 1" clearance from the spring and over an 1" clearance to the wheel well lip.

I plan to mount 255/60 tires on them.