thanks guys .
talked to MT this morning , you can use the 28x10.5 on a narrower rim without too much disadvantage . Also talked to Centreline about custom backspace on their wheel I run , that is doable at no extra charge .
I am leery of running the 9" tyre , especially with a bigger motor under way .
I have only ever run radials , ET street radial , Radial Pro 275 ( poor result) and the last couple of years the Hoosier 275 radial slick with good success .
I also tried a Hoosier 9x30(29.9 tall) but the car wouldn't pull the last 100' or so , only 4.1 gear
the possible extra life would be a bonus

Tex