Ron - When I had a set of the 295/65R15s mounted on 8" rims, the section width (sidewall width) was right @ 12", along w/ the 10" tread width.

I also use to run the Hoosier 91" circ 29" x 9" drag radials on the same wheel size and their sidewall was about 1" narrower, as I recall. If you have MORE than 1/2" clearance inboard & outboard of your Hoosiers now, then the M/Ts should fit.

EDIT: One last comment - the narrowest rim size I'd run either of those particular tires on would be 8"; maybe you can get away squeezing the 9" slick on a 7" rim (and that's not recommended), but the 295/65 needs at least an 8" rim.