good question - i don't have a clue!

how would i be able to tell?

i have an 80 rabbit 1.5l diesel waiting for a 1.6l td swap. i have the motor/turbo & some other parts waiting to be rebuilt to go into the rabbit. i also have the mk2 dash & i know that i'll need a mk2 1.6l td cluster. i'm not sure if i will even use the guages, as i'll need to add a few more & may just use the electronics from the cluster to hook the drivetrain to the new guages in a homemade cluster similar to one a friend made for his car. but i may not add all of the required guages right away (egt, a/f etc) & thus may run the stock cluster & low-no boost during motor breakin etc etc so it'd be good to have it in kmh vs mph. (speedo)

annnnyways - i'll ask around & find out how i'll be able to tell whether i need 1 or 2 plugs.