I snuck my sisters 65 Valiant to Quaker Raceway back in the late 70,s It had the 225 Slant 6 and some decent factory gearing

Boy was that thing Fast for a slant 6

I remember running some mid 18,s maybe even a high 17 on a run

Your newer more smog motor and heavier car will run slower. Im going to guess high 19,s to mid 20,s if you have her running good. mike