The stock converter is your real handicap.IMO We ran a stock from the boneyard 360 magnum with The china RPM knockoff,650dp,3.73 gears,9.5" converter,727 trans,shorty headers single exhaust. Went 13.50's.I also ran this truck in various configurations including a well built 500 OD trans,factory EFI,etc. Little bigger cam and a set of bowl blended R/T heads runs 12.50's @107mph. I'd think you'll see 13.30's as it sit's. A decent converter and 12.90's should be no problem.