mk3 coil in mk1/mk3 ady engine

centre pin where coil lead fit is a negative reading with multi meter is this right or should i change for mk2 as ive heard mk3's can be alot of trouble?

use a MK1 or MK2 coil, much more reliable and it'll work the rev counter properly!
the centre lead will be a pulsed -ve reading, as this earths itself to the spark plugs in order to cause a spark

what does hall sender on dizzy do is that the elec version of contacts?

yeah pretty much it aye, tells the ecu/ign controller where the rotor arm is pointed at