Good useful information but a question... The td42 NA and turbo /turbo intercooled versions ran from late 1980's to 2006..... Was there any major differences between the models? As some gu's had 4.2 intercooled turbo diesel on the door, others didn't, some were referred to as TD-6 intercooled.... What were the differences between these motors? I heard the aerier motors had heavier stronger cranks, then they were lightened for a more nimble feel, some were black tops some were silver tops.... What does all this mean and were there major differences between what was effectively the Same engine?