It does seem that FIA models often have a higher stance than other 289 and 427 cars. I’m not sure if ERA mimics that or not on their FIA model that might give you a clue of how it would work on a 289 street. At least on my 427 that panel in the front of the wheel well that is bowed into the wheel well for seat back clearance was my tight spot. I actually extended the length of my trailing arms slightly to get a little clearance. I was getting some light contact on suspension compression. I went out to look at my car and refresh my memory of where I was making contact at the front and it was a couple of inches above the mid-height of my tire. So, it could be that if the underbody of your car is the same, raising the chassis 1” to 1-1/2” might get a 28” tire in there and down below that area enough that it could miss it OK.
But another thing, I also remember that since I ran a 70 series radial (27” OD again) up front (instead of usual 60 series) I also had a tight area at the bottom rear of the wheel lip when the wheels were turned. I had to shave one side a little. But a 289 body would be so different in the outer body panel there that this may not mean anything.
A 27” tire was basically what a 7.75-15 was close to back in the 60s. An 8.25-15 was 28.5” but generally only full size cars would run something that large in diameter. Some of the Cobra replica manufactures after the 70s actually shrank the wheel well opening on their body bucks/molds so lower profile 25.5” to 26” tires would look correct without a lot of air showing at the top. So I think it may be difficult getting a 28” tire in there. A 215/75-15 is 27.7” diameter and that might be about it with a little luck.