The '69 Super Bee's have a little more rear wheel well clearance than a '69 Road Runner and I only know that 275/60 -15 tires on 10x8x4.5 will barely fit on the rear of a '69 Road Runner/GTX and that is barely. It's no problem on a '69 Super Bee but so close on a RR/GTX that I went with 255/60-15's on the RR and GTX both '68 and '69 and could just get a finger of clearance between the tire and inner fender well. You might want to go to the A12 Registry here http://a12mopar.com/yabb/YaBB.pl as there's a lot of experience with wheel/tire combo's and '69 Super Bees.

http://a12mopar.com/yabb/YaBB.pl