Yes, they can/may/could/should fit.
I have 18x10's on my '69 bird with 275's. Probably could've gone 285's since I cut about 1/2" off the fender lips when we welded them on. I could've fit them without cutting, but felt better with the extra room. I have DSE 2" drop leafs and Hotchkis/DSE 2" drop coils in front.
There should be no difference between the Camaro/Firebird rear quarter and inner fender area, so don't worry about that. I used Camaro inners to repair mine. The rear subrame, trunk, floor, inners, outers, trunk drop offs, quarters, etc. all will fit. Many guys put Camaro quarters on before Firebird qtrs were available back in the day.
If you have the original BOP rearend, you will need different BS than a Chevy since yours is most likely wider, but I've seen/heard different widths all over the map. You're going to have to measure, measure, then measure some more.
I went with a Moser 12 bolt, so I had mine narrowed an extra .75 inch on each side, and my BS is 5.25 for the fat lip look without mini-tubbing the car. Regardless, as long as you nail the BS, you'll fit. You may have to roll the fenders. Also, be aware that your axle is most likely NOT centered so take that into account.
I would guess your BS to be in the 5.75-6" range...give or take.
Here's a pic of mine currently, sorry, just got it out of the garage yesterday so don't have any off the stands ready yet.