You won't use the 1st over, 2nd over. Go read reviews from actual owners, 90% of them say it's useless for anything but a highway OD, with gear splitting too insignificant to produce an ET gain at the track. IMO selling your 727 and doing a 518 would be more cost effective and more useful than the GV. If I was in your shoes I would definitely still consider it.

Also FWIW, I almost never need to downshift to pass with my 1.8L stick shift daily driver. I would have to question the driver if passing downshifts are something you need to worry about with a 400+ cube engine.