Any of the redline products are good just don't use all shock proof heavy. Generally most use 1-1.5 qts heavy and the rest mt90. I have used valvoline,mobil 1, penzoil syncromesh, redline shock proof light weight. They all work but redline seems to be the best.
I think personally the best way to make these transmissions last is to actually change the gear oil sooner than once a decade. I would say once a year at least depending on how much you drive or how hard you drive your car. Also, i am still using lightweight shockproof, but am going to switch and see how the shifting is with mt90/sph vs the spl.
If it will make you feel better Ben i will switch to the mt90 and sph mix when i change my fluids this weekend.