tacho pulses to talk

Hi all me and the better half have a 92 gq patrol did have rb30 in it and 5 speed manual, but they died now has a v6 in it with turbo700 gearbox our problem is cant seem to get the tacho to work. The problem I beleive is that the pulse is different upon enquiry a auto spark agreed and aid 500 dollars can fix it . Any one out there with any Ideas on how he would do this and if there is a easier way.

thanks hope to get a easier fix.