No one answered this, but I would not expect the 60 to change very much no matter what pressure you run if you are not sp[inning the tires. Unless you run nearly flat, all changing pressure does is change the footprint on the ground.
You never gave the starting line RPM when on the trans brake. My guess would be your converter is too tight. Also, you might need more gear or less tire height. What RPM do you cross the finish line at in high gear? How tall are your tires?
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89 LX. 363, single turbo, Super Vic EFI, TFS high port heads by TEA, solid roller, glide. Holley HP EFI. (exact combo varies)