4.10 or 4.30. Or, be a man, and get 4.88's or 5.14's. I ran 3.90's for awhile, and needed more. I found the 4.10 was the best out there. My MPG dropped a little on the highway, and raised a little in the city. Unless you got a blow job under the hood, get the 4.30's. Motive Gear has got it all. Maybe it's me, and maybe the ring and pinon come from the same factory, but I avoid FRPP gears like the plague. I think they are crap, because the two sets I got were damn near impossible to set, and they chattered. I went with Motive Gear, and we had 'em shimmed up and backlashed within minutes. I didn't even break the gears in all the way. No problems with their 3.90's ever. No noise, no chattering, etc. For $200 they better be good!
I've got 4.10s and I can get 25 mpg on the highway running 75mph at 2500rpm. With 4.30s it might raise 150 to 200rpms over 4.10s. So 4.30s are an excellent gear.