Overdrive or don't worry about it? !

abodyjoe said
26" tire:

3.55 @ 70mph = 3250 RPM
2.94 @ 70mph = 2670 RPM

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28" tire:

3.55 @ 70mph = 3000 RPM
2.94 @ 70mph = 2500 RPM

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THIS, OP you are under/ over / around thinking this. There were Gigans of these cars built and DRIVIN ON THE HIGHWAY. Put some decent diameter tires on it and anything 3.55 or higher geared and drive it