The 283 is a good motor and that is what I am putting in my truck. The stock rearends are not noted for going fast. Sixty could have the rpms up. If you want to go faster you can 1) put taller tires on the truck 2) change the rearend ratios to something move highway friendly. 3) put in an overdrive transmission.

Figure out how you are going to use the truck and have fun. Good luck, Wayne