My opinion, heavy truck, stock 318, stock converter and prob. 3.23 gear, and too much carb for your combo, a 600 vac would be a better choice, what size squirters do you have? I would try some different squirter pump cams (slower ramp) and some smaller squirters. After you sort that out you will most likely need to jet it down depending on what you have in there now to help your mid and top end.