66 chev rearend swap

I was looking for some advice for a different rearend for my truck. I have a problem not being able to run down the freeway without the engine screaming at me to find another gear. I have been looking into different trannies and overdrives but this is going to cost me to much right now so in the meantime Im told I might want to swap out the rearend so if anyone can give me advise on something that would work for me I would really appreciate it. If it matters I have a 250 with a 3 speed trans  

Or just swap the ring gear & pinion in your axle.

You should have a wide ratio Muncie, or Saginaw.  Easy enough to tell the difference, by counting the side cover bolts. But, that's beside the point.

You probably have 4.10's, given the year/engine/tranny combo.

Swapping in a set of 3.42's will drop you 5000 rpm @ 60 mph.  3.08's will drop 800 rpm @ 60mph, but you might to find it tricky to start out on uphill grades. 2.73's give you a strong 1000rpm drop, but unless you go to short tires(wich defeats the whole purpose), taking off from a light will be hell on your clutch.


Just $.02 from my end.  
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1949 Chevy 1 1/2ton, home-built hydraulic wrecker.  Rustoleum industrial black, with flames.  Flamethrowers out 5" dual stacks.
1962 Chevy C-20, 402BB, 4-speed, 3.90 positrack. Hauls my camper.... among other things.