I have 28.0/9.0-15 M/T ET Drags on my 66 D/Dart and they barely fit. They are mounted on 15x6 rims that have 3 3/4" offset. I had to add a 0.250 in spacer on the passenger side to keep the tire from rubbing on the S/S spring clamps. The cross sectional width of this setup is about 11 1/4". If I had to order new tires for my car, I'd go 8.5 max on the width for my car. Just check the cross sectional width of the tire you choose. 275/60-15 BFG Drag Radials will not fit. Too much cross section.
There's some pictures on the D/Dart thread of my car with the M/T's on it. No close up though.
Since it's going on a 66 Valiant and if it's used on the street, how about some cheater slicks. M&H Racemaster has some period correct cheater slicks. Radir also has them. Firestone (Coker) has some pie crust cheater slicks that look pretty cool. There's also a company that makes recap pie crust cheater slicks. Can't remember it's name though.
Good luck
