If you are using a SBF, why not consider a 6-speed. I have a source who can get you a custom-prepared Getrag 01E, 6-speed transaxle, like mine, which is beefed-up and rebuilt (upgraded rear main bearings, altered spigot shaft and altered clutch fork) to comfortably handle 400 HP.
My 6-speed transaxle has a 3.50 1st gear; 1.888 2nd gear; 1.230 3rd gear; 0.933 4th gear; 0.729 5th gear with a 0.600 6th gear and a final drive of 3.875. With the engine at 5500 rpm, the gears are nicely spaced as follows: 1st Gear=32 mph, 2nd Gear=60 mph, 3rd Gear=91 mph, 4th Gear=120 mph, 5th Gear=154 mph and 6th Gear=187 mph.
If anyone is interested, let me know. It can be ordered with SBF adapter, clutch, flywheel, pressure plate, throw-out bearing, clutch slave cylinder, starter, etc...everything needed.