See the small size Jack plug to joint the head unit to the min lead and the 4 pin connector 

Has plenty of wire to reach through the bulkhead 

Not sure of the make but definitely not laser pro park which has a bigger head unit 

Untested as there is nothing to test it on !

A whole kit is about £500 if you can get it nowadays so hoping someone has a unit with a dodgy head unit that this will bring back to life