I had always used a 12N7-4A battery (center), which is a 7 amp kickstart model used in the '71 & '72 FX and '70-78 XLCH. It would fit in the horseshoe tank, but needed a 2 X 4 to sit on to raise it up, and a 1 X 4 placed between it and the fender (left). There wasn't space for the hold-down rods, so the battery would vibrate around and the overflow hose would come off, and eventually the chrome was eaten away in spots on the tank and primary chain housing by the acid. Aside from the corrosion damage, I wanted a new oil tank since the old one had non-removeable HD type nipples welded onto it.  Unless you used steel or braided lines you had to do what I had done... flare some copper tubing and slip some 3/8" ID hose over it and clamp it down. This time I got a tank with 1/8" NPT threads so I could use hose barbs. I did some surfing and found WestCo Battery's website, a manufacturer of sealed AGM (Absorbed fiberGlass Mat) batteries. The only Harley batteries they appear to sell are for electric start, so the model I chose was the 12V7LB (right), which is a 7 amp battery made for Hondas (don't say it!). I take it the general adaptation for a 12 volt battery in a horseshoe tank is to use a 12N5.5A-3B lead-acid type in an aftermarket holder that raises it to the 8 5/8" height of the regular 6 volt. The new leakproof battery had different dimensions (plus a 1.5 amp increase in capacity), so I had to construct some type of custom holder for it. I'm sure a sheetmetal shop would have been up to the task, but I had a bandsaw and drillpress, and a weekend without anything else to do since the tanks and fenders were at the painter's and the engine was still at Andy's.

Here's what I came up with. I used 1 1/2" X 1/8" aluminum angle, 3/4" X 1/16"aluminum tubing, 10-24 threaded rod and of course 10-24 locknuts. The 3/8" rubber pad's original function was 18" flooring squares in a workout gym, but it made an excellent shock absorbing spacer when cut with a razor knife to the proper size. Here's the dimensions and the parts layout if your curious about the holder's construction.

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