Is your truck a pre 80? Not sure of exact year split. There is a base for driver side try needs to welded on to tray. Can be bolted, but I hear mine bonce when I hit good bumps. Going to weld when I get a chance.
Any way LMC has the base, part# 38-6313.
73-80 and 81+ is the split.
Just cut the old one out and bolt it to the side bracket.
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That is where a button head comes in.If you bolt the tray to the support bracket, make sure that it doesn't rub a hole in the battery. That is why the factory welded them together.