Click on a pic to enlarge:

Click on a pic to enlarge:

Triangle shaped side, battery box built into it. Drain plug (704) on (R) bottom of tank.
Oil filler neck is shorter than the -80 tank. It's not clear what the actual oil amount is for the tank.

¹⁾

Oil Tank Cover Mounting Brackets on the Frame:
The 80-81 frame will not take the 79 cover.
The 79 frame has welded on tabs for that cover (third pic below) , and a welded in place nut for the bottom mounting bolt, that the 80 frame does not have. ^{2)
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Triangle shaped side, battery box built into it. Drain plug (704) on (R) side of tank at the bottom.

79-81 tanks are 15“ between the hole centers. ⁶⁾