Rear clearance question

Got Chevy '66 hardtop. I want to put at a 9.5 inch wide tire on the back (17x10, 275's) with a 2 inch drop. I hear the max on stock is 255. So I think I got no choice but to expand or weld on a "mini tub". Will i have to sacrifice my back seat and the stock gas tank? I was going to buy a 4-link suspension set up but do I still need it after the modified "tub". Is this a labor intensive and expensive? Is there any sheet metal kits out on the market for modified "tubs". Thanks alot!!!

First, I believe 275's are 10.8-10.9" section width, and 255 is right around 10", and you say you want to run a 9.5. You should be able to run 9.5 in stock tubs and without moving leafs. It's all in the rim backspacing. If you go to a 4 link, you will pick up even more space because it gets the leaf springs out of the way, which cause interference in stock wheel housings because of where it is located. If all you want is 9.5, You won't have any fabbing involved...just measuring.
And a minitub will not forfeit your back seat or affect your gas tank. Minitub usually involves taking it just to the rails on these cars.

Do I need to be aware of the width of rear axle?

so what is the biggest rim and tire u can fit in a stock 66 nova
wheelwell
rim size
tire size
backspace
i would like to know also
i was going to get a 7in. rim but if i could go bigger the better
chris