295/50/15's will it work??

The spacer will push the tires outside the fender....

A 295 is a large tire to put in with out beating the inner fenders and rolling the lips. It would better fit on a 15" x 10" with 6.5" backspace.

Besides the backspace issue, a 295 section tire is WAY too wide to be mounted on an 8" wheel if you want to effectively put all the tread flat on the ground. It should be on at least a 9.5" wide wheel, the 10" suggested above would be even better. While you may make it fit the car, that doesn't mean that the actual traction you get is gonna be better because the bigger tire isn't optimized when it's mounted on a rim that's too narrow for it.

If I were made out of money I'd mini-tub mine and put some 305 or 315s on the back.

I've got 295-50-15's on 15x8 inch Weld Draglites with 4.5 inch backspacing. They do not rub the inner rear quarters at all, but they will rub the exterior quarter panels unless you install a pair of Air Lift's air bags inside the rear springs. These will help out at the dragstrip too. As previously stated, they can be mounted on the wider rims, but I'm not sure of the backspacing. Also, I'm not too sure about the 5.5 inch backspacing on your wheels. I think that you'll have problems with it rubbing on the inner quarter panels with those.

FYI, the 8 inch rim width is the smallest size that is recommended by B.F. Goodrich to mount these tires. Mine also look like all of their tread is touching the ground.

Here's a picture of mine.....