Another "Will these fit?": 18" Mustang wheels

So I did search and was able to find a couple posts by members running 18" Mustang wheels but I wanted to make sure these specific ones would fit on my 1970 Duster. It is of course converted to 5x4.5" bolt pattern all around with '73-up front discs, also has an early B-body 8 3/4" rear so it's a tad wider than an A-body rear axle. I'm mostly curious about the backspacing (these are 5.95"), I've read the 17s can have clearance issues with the tie rod ends which is one reason I want to use 18s, also slightly better tire availability in the sizes I want. Thinking about going 255/40-18 in the front, will those be too big? And 275/40-18 for the rears...

18x10/18x9 Wheels for Ford Mustang FR500 FR05B Black Rims SET