even better is to find a 4.10 or 3.9 geared one. They are around. I did that swap on my 5.26 and it was a huge improvement. I can go 60 now without stressing the motor (a newer 292).
And it is an easy swap - unbolt the old cover - let the goo out - unhook front ujoint - undo the axles and pull them out a few inches. Then unbolt the old gear set, and bolt in the new one, replace axles and covers. Instant gearing.
However, be careful of the axle seals. Mine soon went out (but could have been about to go anyway) and had to be replaced, but was not hard - and the seals were $7 a throw at NAPA. (Fits like 47-73 chevy truck....)
