new vapor gauge installed, question on rpm's

hi all,
am very happy w/my vapor gauge (75-704) unit. got everything hooked up and am fine tuning the unit. because i've already removed my orig gauge cluster, i have no baseline to measure the accuracy of my new tach.
i searched and found no mention of rpms in the final gear vs. speed. what i'm asking is can someone tell me what the rpm's are at 75mph? and yes, i'm using stock tire sizes.
thanks!

 

Shirley's a 650, but she sits @ 6k doing 75 in 5th.

 

Shirley's a 650, but she sits @ 6k doing 75 in 5th.

 

the tach is right or really really wrong, all it does is count the pulses from the coils and does some math.
does it read smoothly and seem right at idle ?
wrapped on the spark plug wire or direct to coil?

 

thanks for responding guys!
actually the vapor tach is affected by "engine noise" and was perfectly tracking the orig tach up to 4k rpms (i had 'em both working at once, wasn't willing to remove the atari til i confirmed performance on the vapor).
the vapor tach can be "tuned" by adjusting the amount of wraps it's positive wire makes around a plug wire. i think i'm close but need someone to tell me what rpms are at 75mph so i can confirm the vapor's settings.
thanks!

 

i should've added that direct connection to coil is an option but if i can make the spark plug wire wrap method work it's a lot easier due to the location. vapor (trail tech) says direct connection to coil may or may not relieve the issue. adjusting number of wraps on plug wire is first step to diagnose. the surging above 4k is gone now but i don't know if it's presenting accurate info or not. can't remember what rpms were at highway speeds.
thanks.