Will it fit? L60-15 Polyglas GT on 15x8 steel 4" BS

in my experience;
as to Polyglass tires;
>have terrible traction, even with slapper-bars. They were short-time-on the-market for a reason.
>They also have a wider footprint than a radial, and so will contact the fender-lip sooner than radial which rolls over.
>they are heavy, and on a steel wheel will ride HARD, like a tank,hard.
>wait until you have to change lanes in a hurry on the PGs; you will be plowing into curbs on a regular basis, and or spinning out.
This has been my experience.

The Duster tubs (about same as on my 68 Barracuda,) will accept 295/50-15 Radials on 10" wheels (at 24psi for long life), easy enough.
>I highly recommend alloy wheels, offset springs, and a narrowed-to-fit any standard 4.5bs wheel, into, that is to say; inside of, the stock tubs..
>Size for size steel Rally wheels weigh about double of alloys.
>295 BFG/Coopers on 10s only have traction until you cook them, or for the duration of the first summer whichever comes first; then they are still better than the Ls. But they can still go five or more years on the street and drift very predictably with no sudden surprises. And they have a pretty good sideways patch, for those times you come into a turn just a lil too hot; just toe the clutch or feather the throttle and let the tires get back to roadspeed.
Coming in too hot on the L60s; they will just skate and skate... until they or the car, bounces off something.
Mind you, the last time I was on PGs was about 1977..............