I was thinking perhaps it could be a leaking head gasket on the passenger side bank. Why not replace the head gaskets? From what I understand, the Commando came with longer valve springs then the 2 barrel version. What will putting 340 valve springs on the engine do? Isn't anything related to 340's in the unobtanium price range?
Thanks for the ongoing help
Leaking on all cylinders on one bank, to cause lower compression, is next to impossible. Leaking head gaskets are usually one cylinder or possibly 2 adjoining cylinders and rarely are they just 10 or so pounds lower than the rest.