Yes, if it is an open diff, it will be/act just like the stock one you have now.

You should see an increase in mpg since the taller gears will get you moving easier. It still wont be like your Vette, but it should feel like you increased the HP some, and you will be getting the most out of the upgrades you have already made to the engine.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed