[Chuck78]

Originally Posted by Chevy Fleetside

255/60/15 up front 275's rear.

I think if you have a 70 series tire mixed with a 60's series tire it might look odd.

I think with a 60 series 245 up front on mine, it looks really odd, even after I lowered the front suspension (torsion bars, adjusts with the crank of a ratchet) quite a bit lower...

The 275/60 & 235/70 have nearly the exact same sidewall height. Guys with 275/60's on musclecars have complained on forums that the rear squirms as if it's riding on balloons, however. Mine seem to look pretty correct aesthetically on the rear.
The front wheelwells are much larger and more open than the rears, and my 245/60R15's at 26" tall look anemic compared to the 28" tall 275/60 rears.

I was afraid the 255/60R15 would still look too tiny. I know it will give the better steering response and dry grip. The 235/70 will give better wet grip and ride height. I'm still not convinced that it won't fill the wheel well better / more appropriately than the 255/60R15... I'll have to stare at your photo some more, Chevy Fleetside.