Carb CFM recommendations

Since you don't care about performance, any carb will do.

For what its worth, when I lived in Colorado, I started out with a 318 in my 67 Barracuda....that motor I had a Holley 650dp on it, and it was happy....Drove it from Golden to Greeley all the time. This was back when she was slow (high 16's in the 1/4).....She was a good daily driver.