This was kind of an unintended project. My Supra came with an Optima battery that wouldn't hold a charge very well. I am priming 2 fuel pumps when the ignition turns on, and plan on having a subwoofer so I wanted a good battery. I've had good luck with Odyssey in the past on my 3000gt. So I bought the PC1500 battery for my Supra. According to their fitment guide I also needed the spacer as their battery is a little shorter.
The Odyssey battery came and it was too large for the oem tray. The oem mounting bracket also is too wide for the battery and there was no room to mount the overflow tank to the right side of the battery like it was with the Optima. My oem tray was cracked, and the metal inserts were pretty rusty. So I hacked it up just so I could move the battery around and see if I could make room for everything if I made a custom tray. There was just enough room.
I ordered everything from Amazon. I screwed up and ordered Left Hand Threaded rod initially by mistake. Cost will be around $100 when all is said and done. You may be able to find the bolts cheaper elsewhere, or in smaller quantity.
The first thing I did was clean up the body underneath the factory tray. The bolts that held the tray down were rusty along with the metal sleeves inside tray. This rust transferred over to the body. I had no choice but to sand it away. I touched the area up with some primer and gloss white Rustoleum Professional spray paint. Obviously it's not an exact match to Supra white, but it blends in decent enough for something that is going to be mostly hidden by a battery.
The aluminum plate was $38 so I didn't want to just wing it. I started with some cardboard to mock up the plate. Then when I was happy with that I made the template out of wood. This way I could confirm I had the screw holes perfect. When I was happy with fitment, I cut the aluminum. I used my jig saw with a metal blade. I clamped a thick ruler to the place to serve as a guide. Some of my cuts did come out a little wavy, but I smoothed them out on my bench sander. Afterwards I wet sanded the plate with some 500 grit to kind of give it a brushed look.
Here is the aluminum tray bolted in place before I drilled and tapped the threaded rod holes. It's not bolted right on top of the chassis. The area it bolts to has some humps so a flat piece of aluminum wouldn't bolt to it well. I used some of the scrap aluminum to cut out 3 big thick washers to act as spacers. This allows it to lay flat. Originally it did slant slightly towards the passenger side. The oem tray did too. I assume this is by design as the oem tray has a drain hose on that side. To make it more level I added 2 stainless washers to that side. This is why I ended up ordering 2 different size bolts (30mm and 35mm). I had ordered 30mm originally and after adding the 2 washers I needed a longer bolt. If I could go back in time I would have just ordered 35mm length bolts to begin with.
Here is is all together. For the threaded rods I did tap the aluminum but I also threaded the rod past the plate and sandwiched a nut on each side of the plate to make it even stronger. I'm not using the Odyssey spacer so the battery sits a little lower than oem. Everything is nice and snug. My car starts so much better with this Odyssey battery, and if it's anything like the one in my 3000gt it should be good for 8+ years.
Since I had success with my Supra tray I finally decided to tackle the tie down on my 3000gt. I've had this Odyssey battery forever without it being tied down. It is shorter than the factory battery so the factory tie down does not work. Back when I ran my metal hood I would place a folded microfiber towel on top of the battery to keep the terminals protected. With the carbon hood it wasn't needed. I bent my own piece of 1/4" thick aluminum stock to make it clamp lower. I cut and tapped the threaded rod so that I could move it in closer.