That record was set, in the summer that I had that trans out maybe half a dozen times, making mods to street slick-shift second and third,as well as to run synthetic,and still have it shift at 7000.
It was set using a drive-on hoist, and by this time I knew every tool I would need, so they were all on the tool-cart.
And finally, this was with a Passon aluminum case, and the GV aluminum tail;so tranny was at 85# with oil, and therefore no trans-jack required.Plus I was 10 years younger,lol.
I never could make it like synthetic all that much. I currently run 50/50 ATF/80W90 gear oil.It shifts like lightning.It works really great with 100% ATF, but that's hard on the cluster-pin.So I put some EP oil in there to ease her pain.As to shift-speed, I couldn't really tell the difference anymore, the slick-shift mods were far more effective than I imagined they would be.