Trouble finding with search words- wheel/tire combos

Yes, I know it's been brought up many many times over the years, and I just spent 2 hours using different search words trying to locate this info. This is not the first night I've spent hours researching this topic online. I finally have to give up and ask you all for help.

Therefore, if you could be patient with this question I would be much appreciative. '68 RR; looking to put 15" steelies all around (will purchase Wheel Vintiques through Summit I guess); most likely going diamond back redlines; I'm pretty set on going 275/60's in the rear but not sure if 4" or 4.5" back spacing is appropriate.

Front- undecided on 235/255 60's or go 225/235 70's. Also back spacing.

Thoughts and pictures would be great before I drop a lot of money (at least on my teacher's salary) on these. Thank you in advance!

enter B body wheels and tires in the google search box.

Here is my setup.

Rear Cragar SS 15x8 with 4.25 backspacing. Tires are 275/60/15.

Front Cragar SS 15x7 with 4 backspacing. Tires are 225/70/15.

Another angle

That would explain it... I was searching on this site and finding it very difficult. I'll do that tonight.

Thanks for the pics. It appears the taller, slightly thinner fronts fill up the wheel well better than a 60 series. Thank you!