Long 18mm wrench or socket on breaker bar on the center bolt head and remove the belt. This is a left hand thread bolt so pressure is toward the firewall to relieve tension and slide the belt off. Note: the bar will travel further toward the front as the spring tension is released after the belt is off so allow hand clearance for overtravel on release. Then the bolt can be removed with a clockwise rotation.
I would have said the same as Ronnie and you have already swapped the big players. Long shot, but is the jumper cover on the ALDL connector? The other curious thing is the cluster was possibly repaired and maybe a fault is still present?