The PPG helical syncro box should not be mated to a 3.90 FD if you're autocrossing, IMO. The gaps between ratios is too great and 2nd gear is simply too tall. You'll be trying to row first and second gears but finding a 40% ratio change cramping your style. Nay, the PPG ratios are pretty poor for autocross. For those building track monsters, it does bridge the gap to the RA 5th gear rather nicely.
IMO, the RA close ratio 5-speed gear set will be strong enough for the NA EZ30R and afford 70 miles per hour in second gear (with a slightly increased redline). The reality is that I'll be running 25.5 inch tall tires to get the tire width that I need.
Finally, price is a concern. PPG = ouch!