I think the section width on those on an 8" rim is about 11.8", shouldn't be a problem there, but check your 275s against the front of the wheel opening. You'll need another 1/2" or so for the height difference between a 29" tire and your 275s, which should be about 28". You may need to space the front hangers back from the unibody a little; or pie-cut the opening flange to retain a shorter wheelbase if the car's already modified
I ran 295/50R15s on 15x8, 4.5BS on my '68 Hemi RR and there was plenty of room all around, stock springs & ride height.
Lately I've been messing around with the idea of 29" or 30" Drag Radials with an 11.8" section on a Duster, which requires some opening-up of the front and the top, and a 4.5-5.0 BS, springs moved in 3/4". You have a lot more room.