Biggest Rear tire setup on stock 68 dart 14" wheel

I have been searching and find a lot of conflicting answers. Tire sizes are not really my specialty. This is a 270. It has the stock springs, 4 doors, and I'm sure it has the 7.something rear end, and a slant 6.

The only thing consistant I found is a 255 60/15 would fit,and 225 70/15.

But I see a lot of things working for 15's. I want similar sizing from my 14" wheels I have, but have no idea how the sizes convert when you go down 1".

They are a set of 14" x 7" SBP American Racing Outlaw II's.
4" backspace
0 offset


I just need to know what will fill up the back as close as I can get while not hitting anything. I want it raked, so I don't care about that. If the rear needs to be lifted a couple, I can do that too, but prefer to see how big a tire will fit with the stock setup. It seems the lip on the inside of the panel closest to the door will be an issue for a larger tire. Do people usually cut that? I can do that as well.

They are also only going in the back. The front is staying as is for now, so I'm not worried about having all 4 tires the same.