What would look and fit better?

[HELLCAMINO]

These are going on my 71 Chevelle

An 18x8.5 front and 18x10.5 rear

Nitto 555's
Either 245/40's and 285/40's
OR
255/45's and 295/45's

[Schubitzky]

I can't speak much on fit for your chevelle, but personally I think the 40 series sidewall looks better, and more than likely performs better. The tire won't roll over as much with the shorter sidewall. As long as the tire isn't too short for you. The 45 series is about 1-3/8" taller than the 40s. 25.6" vs 26.9" on the front and 26.9" vs 28.3" on the rear. I've got 245/40 and 275/40 BFGs on my car and I think they're 25.5" tall or so.

You gonna have that thing ready for Hershey? I've got about another weekends worth of work to do on mine, but I hope to be there both days (as long as everything I've done works with no problems).

[HELLCAMINO]

I think these A bodys need a taller tire to look right, that is why I am contemplating the 45 series to fill the wheel well better. The Chevelle most likely will not be ready for the March race, the Elco will be there though.

[CampbellshotrodsAZ]

I did the 2nd option you listed, the 45 series on a 71 Chevelle I did a few years ago and it filled the wheelwell perfectly. I don't have a picture readily available, I'll have to dig one up later.