Going with an overdrive trans will drop your RPMs and make your ride way more highway friendly. Another option is do a late model rearend swap. A 14 bolt rear from a dually truck is popular swap. A Dana 60 from a Dodge/Ford van is also a popular swap too.

14 bolt http://s1074.beta.photobucket.com/u...amp;_suid=136167734275303977352668859631


1954 3600 Chevy Truck
"The Fake Truck"
In the Stovebolt Gallery
More pix on Photobucket