Fleetstar oil cooler

Hi....I have a 1974 2050A Fleetstar dump truck with the DV550 diesel engine. My oil cooler gadket has failed and I need to replace with some original gaskets I found in Saskatchewan. My question is.....do I have to remove anything before I attempt to undo all the retaining bolts. There seems to be no roomroom against frame. Ive been unable to find a shop manual for this truck. Instructions for tractor oil cooler on same engine dont seem to make sense in truck application. Anybody replaced this gasket?