Click on a pic to enlarge:

Click on a pic to enlarge:

Triangle shaped side, battery box built into it. The drain plug (704) is on the left side of the bike on the side near the 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)
3) 4) 5)}

Triangle shaped side, battery box built into it. The drain plug (704) on is on the left side of the bike at the bottom.
There is an extra mounting tab welded to the top inner side of the tank in front of the vent nipple.
An “L” shaped bracket (66279-80) is attached there that is slightly curved on the bottom to sit on the right frame tube with a pad under the bracket.
The left side is exposed without a cover and has a “Made in USA” transfer emblem in the center.

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

Mounting tabs repaired on a 1980 frame:
⁷⁾