Torque converter
Having the right converter for your combo is worth a lot.
Our combinations are very similar, horsepower, weight, shift RPM and short block. I run a 3.91 gear and a 26" tire. My car consistently 60's in the low 1.5s on an 8" slick.
I run a 904 with about a 3500 stall, and I have a transbrake just for disclosure. I got my converter from Lenny at Ultimate. I leave between 2700 and 3000. I have launched it higher, but the car didn't pick up.
Given any thought to gearing it up or running a 26" tire? I've never put together a combo that did its best 60' with a 28" tire.
What kind of tire are you running? I have found a lot of Hoosier tires to have too soft a sidewall and eat 60'. However, I am currently running their 8" stiff sidewall slick and it works great.