Lets see some pics? It must be tubbed out like this one by Mark Burton that is tubbed, custom frame, sectioned quarters to fit the 33" tall tires in teh wheel well:
Ive had fats and skinnys on all my buicks, GN included, I do however usually run 5's or 6's up front ,just feels way more stable and much better stoping distance if needed, buildn a new 12bolt now that will allow me to run 10in torq thurst with a 3 3/4 back space, gonna have a wicked deep dish, also gonna run a set of the new direct bolt cragar ss's 10in with bias ply 275 60 protracs for the old school vibe
I have an older car than most of you but look at my 53 here. I think the stance is OK,slightly lower in front. Lots of frame, suspension work on this one but rides Super smooth.
Buick and Futura are uncut. Camaro (unfinished waiting for body jail) rear floors were toast. I was going to mini-tub. Now complete back half. I'll be running 315/60s. Enough room for 7" more in case I get the urge.
You are one, ummmmmm, "talented" guy, Jerry ..... On a muscle car type machine, I think you should be able to run at least 10" wide rims on the rear, so whatever it takes to get that back there whether it be stock or mini tubbed and lowered is my preference.
