What kind of revs do your cars do? Cause my car is quite the high rever its about 120km/h @ 4000 does that sound correct? sorry I can't convert it can't remember how to.

Thanks.

 

i rev to about 3400 when im kickin about 85 on the freeway, in 5th

 

http://www.psinvention.com/zoetic/convert.htm

120 Kph = ~74.5 Mph

That does seem a bit high, but we won't know with knowing which transmission and differential gears you have.

 

That speed and rpm figures out to be a 3.9 rear (stock on 81-83 cars) and in 4th gear 1:1 ratio, or if you have an auto transmission that would be 3rd gear 1:1 ratio.

3984rpm at 75mph with stock tire size.

5-speed on the early or later 280ZX should be well below that rpm no matter what rear gears you have.