I like the idea of 10” wide with 6” backspace

And running the 285’s up front

Is this car painted yet?

If not, lip the top front fender lips start. Roller style with baseball bat or tool.

I thought Dan with his blue 68 RR had over 275’s on his.

I think the Hotchkis 70 Taxicab had some wide tires up front.

Fit these tire and rims before paint.

I can fit 275/40/17 on my A-body Barracuda. I don’t have first hand info on a 68-70 RR, but you should be able to fit more than I can.