I run the nitto 305/45/18 drag radials on an 18x10 rim....no track times yet but I've read about a few cars running High tens, low 11s w/these...
I think a popular hot rodding article on this car said it ran low 11s:
http://www.yearone.com/enthusiast.asp?enl=1&enlURL=enthusiast/articles/chevelle/chevelle.asp
This rim/tire combo would allow you to run 12" rotors and still have a little side wall (45 series vs 35 or 40). I'm sure you would 60 ft better w/a 15" rim and a 60 or 65 series tire but this may be a good compromise.
