1973 Scamp ?

Is that 49.5” width just the housing? Or is that wheel mounting surface to wheel mounting surface?

Either way I tend to agree, that’s probably custom wheel territory.

As for what will fit it will depend on your car, but 275’s are possible on the Dart/Scamp bodies with the 1/2” offset. It depends on what your inner wheel well to quarter lip measurement is. Section width on a 275 is about 11”, so you’ll need at least 12” in the wheel well to clear it. That’s about where your car should be, but body tolerances vary. If you’re willing to do a little trimming on the quarter lip it’ll work, if you’re not then hopefully your car rolled down the line on a generous day for wheel well tolerances.

The 27” wheel shouldn’t be a problem, it will be close but should clear. Worst case you may need to shim the front spring hangers back a little bit. But with SS springs probably not.

You didn’t mention what diameter rims you plan on using, which will determine the width you need. For 15’s you can put a 275 on a 15x8, no problem. If you run 17’s you need a 17x9, same for 18’s. With either of those you’d probably be better off with a 9.5”, but the 9” will work.