73 Duster rear fitment

I'm looking at getting some new wheels and tires for my 73 Duster but I'm not sure about fitment. The rear wheels I want are American Racing VN10558065B American Racing VN105 Torq-Thrust D Black Wheels with Machined Lips | Summit Racing. They are 15x8 w/4 1/2" back spacing BBP.

The tires I want to run are Mickey Thompson 3451 Mickey Thompson ET Street S/S Tires | Summit Racing. They are 275/50-15.

The above tires have a 11.10" section width and by my calculations with the above wheel the tire would extend inboard from the axle mounting point 2.05". I'm thinking that this might be 1" too much and will have to get a smaller wheel/tire combo or a different wheel with less backspacing but I'm not sure without mocking one up, which I don't have. Is my math right and what is the max backspacing for a 73 Duster?