My tach is a bit wonky because (I believe) of the aftermarket ingition setup on it (Jacobs)

I'm trying to figure out if it is accurate...

What do you rev at in 4th gear? (1:1 ratio) at say 60mph...

I have a r151f so if we do 4th gear all the trannys should be the same...as long as they are manual...

According to this gear calcualtor my tach is reading wrong...in fifth I'm around 3k rpm at 65......

http://www.grimmjeeper.com/gears.html

Please state your gear ratio and tire size