I've got a '71 Dart with an 8.75", stock wheelwells, fenders, etc.
I can fit a MT ET Street 26*10.5 (same as 26*8 slick) on a 15*8" wheel with 5.5' backspace and a 3/16" spacer, and it is very tight up against the spring and fender lip both.
I don't think you'll be able to fit that 10"...