I have an SM319 overdrive trans and 3.90 gears in the rearend. I also have a taller tire that stock, 30" vs the 27" stock size. It's somewhat hard to hear it happen in the vid, but I did let it drop into 2nd-over before I went for 3rd-over.
I'm very pleased with the combo, I can run highway speeds without getting over 2700 rpm (approx 75 mph) and still have some to spare.
