Our friend Gary Mattson of Simi Valley, California, has a fundamental problem. He doesn't want his new Optima dry-cell battery falling into the cooling fan. The factory battery tray uses a battery lip hold-down, which works well with Autolite Sta-Ful reproductions and many aftermarket batteries. But there are now aftermarket lead/acid batteries, not to mention Optima dry-cell batteries, which require a top-mount battery tray.
For those who aren't concerned with originality, Virginia Classic Mustang offers a top-mount battery tray for '65-'66 models, like those from the factory with '67-and-later Mustangs. This easy swap is accomplished in about 20 minutes and it keeps your Optima battery in place.
Here's the PE-13 top-mount battery tray kit from Virginia Classic Mustang-battery not included. Everything you need is here, including installation hardware. Virginia Classic Mustang also offers the AMK Products' kit, which is dead-on accurate to original equipment. The PE-13 kit is close to OEM in appearance, but cadmium-plated for corrosion resistance. | 
The factory '65-'66 Mustang battery tray utilizes a screw-down clamp that retains the battery at a base lip. Nearly all lead-acid batteries had this lip until approximately 10 years ago. Only a few replacement batteries have it now. Unless you're concerned about originality, Virginia Classic Mustang has a solution with its top-mount battery tray for '65-'66 Mustangs. |  |
To access the battery-tray mounting hardware, the right-side bumper bracket must be disconnected from the framerail. This moves the bumper bracket far enough from the frame-rail to access the bracket bolts, which are behind the bumper bracket. You need a 11/42-inch socket for this operation. | 
This is the view from underneath. Two flange nuts retain the battery tray as shown. There are two different kinds of bolts: a carriage bolt and a conventional body bolt with a star washer. | 
Lift the battery tray out like this, taking care not to damage the paint. If you have any corrosion or rust-through issues, now is the time to fix them. Virginia Classic Mustang can supply an inner fender apron if there are rust problems. |
We opted for the PE-13 kit and wove in some improvements of our own. Large fender washers provide support and reduce the risk of corrosion underneath. A washer gives nuts and bolts a surface to bear against. | 
This is the view from above: one carriage bolt and one conventional body bolt. Tighten the body bolt from above and the carriage bolt/nut from underneath. We suggest the use of 3M rope caulk between the battery tray and body for corrosion resistance. | 
Body bolts and tinnerman's nuts retain the battery tray at the framerail. Tinnerman's nuts clip to the battery tray support bracket. |
Battery hold-down studs attach from the inside out or the outside in. The choice is yours. The trick is keeping them in place while you're installing the top mount. | 
If you run out of threads due to battery height, use cadmium-plated flat washers beneath the nuts. Regardless, this is a good idea to protect the coating on the hold-down. | |