I'm not sure the question was answered as far as speed. No it will not go any faster or slower. The rear end ratio determines the speed. Unless you install an overdrive be it an automatic as mentioned previously or a manual with OD you won't change anything. Your existing transmission is 1:1 in high gear and so is a PG.
Fred

Last edited by rfs56trk; 03/12/2014 4:08 PM.
1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine