Wheel Size Question.

Hello,
I recently purchased a 1967 Barracuda Formula S (273) and I am looking to purchase some 15 x 7 SBP Cragers. Summit Racing has them and I want to make sure that I am getting the correct size for fitment. The ones I am looking at have a backspace of 4.125" and an offset of +3 mm. Could someone let me know if these are the correct size. Also, I would appreciate some suggestions as to what size tire to get. I live North of NYC and I plan to set up the suspension to take advantage of the beautiful winding country roads and switchbacks up here. I really want to emphasize the "S". Before I start tweaking the suspension I want to get some proper performance tires on her. Appreciate any help. Thanks.Cuda 2.jpg