I just put my tach in the gauge cluster and i'm wondering... is it reading really low? it reads 500 at idle and usually 2k to 2.5k at cruise. is this normal or do i have a tach that is reading incorrectly? this is on a stock 78 350.

500 is a little low for idle, but not a problem.
2000 to 2500 is also the right speed for the highway, depending on what gears you have.
If they are 3.73 or 4.11 then it's reading too low. If they are in the 2.41 to 3.08 range then you are fine.
Give us an exact reading, what speed at 2000 rpm, what rpm at 60 mph, and we'll be able to help more.

speed at 2000 is 65, rpm at 60 is about 1600-1700. Thanks

another question... is the tach current driven, pulse driven, or volt driven?

ttt

Sounds about right with a stock setup. 500 idle is ok. freeway gears. 2 series I suspect..

how do i find out what gears i have? is there something stamped on the diff? or do i have to look at my build sheet? (i think i lost it! :o )