OPTIMA Batteries D34/78 YellowTop AGM Battery - 750 CCA, Dual Terminal, Maintenance Free for Cars, Trucks & SUVs | High Performance & Versatile Mounting | Perfect for Off-Road, Marine & RV Use

Fit just fine in my 2000 mustang GT battery holder. No modification needed. No clearance issues etc. I should have bought years ago.The one I got is: Optima Batteries 8014-045 D34/78 YellowTop Dual Purpose BatteryThe battery was about 1mm longer than the tray (from front to rear of car vs left to right), but the tray just stretches out to accommodate. I laughed and said to myself - "Are you serious?!? that's what I was all worried about?!? Lol!" "Good grief - this fit just fine!!! Lol" :-)1st pic shows Mustang2nd pic is looking at battery from drivers side - it shows how the tray stretches to accommodate the 1mm increase in size3rd shows from the drivers side looking at the front of the battery in the mustang - the thing to notice is that the front side didn't need to stretch since it's already stretched on the back side4th pic shows mustang from the front and how it's installed without the blue adapter, without the large yellow tray adapter, and without the larger of the 2 red adapters (I left them on top to show how they're not used)5th picture is from the drivers side looking over the battery to show how I used the red clip that came with the Optima. This red clip is the same as the stock black clip. But the new one looks nicer.6th picture is from the front at headlight level - they show how I didn't run into any clearance issues.7th shows no clearance issue.The pictures help.See, the Optima site doesn't list it as fitting in the 2000 mustang GT. But yet we all know people put them in their mustangs... So the discrepancy between the 2 kept me from buying for a long time.But all you do is drop it in, and lock it down. In hindsight, it was really no different than any other battery I have ever installed.I used the new clamp that came with the battery vs the factory because because the new one was clean, red, and looked cool, but it was identical in shape to the factory clamp.There were a few other clamp items (blue tray items) for applications in other vehicle types, and they caught me off guard and so I tried to use all of them - partly because I thought they looked cool, but most because I didn't realize that they're actually for different vehicles; it ended up just being the red one, which was the same as the factory black clip that came with the mustang. The other ones would raise the battery with no benefit. I don't remember if there were any clearance issues if it was raised, but don't bother with them unless you're just having fun with the battery changing project and just want to see. You might save them in case you ever get a new car and want to bring the battery - Optima batteries are notorious for lasting a super long time.But yeah - the yellow top Optima fit just fine in 2000 mustang GT.I was all worried that I was going to need to get an F150 tray from a salvage yard (which was a pretty neat idea that someone had done successfully), or order a new cool fancy tray (but those aren't cheap). Neither are necessary, but they're good to know because the knowledge helps guarantee that can somehow fit if your experience is somehow different than mine. But you won't need to do it.You can still do stuff like that it you want, but do it after you put your battery in - because if your tray is the hard plastic one like mine, there is absolutely no problem putting it in. No modification to your tray is needed.I was very happy about how easily it went in.Can't believe I waffled for years over getting one.The low price on Amazon helped too. The absolute best battery I could get otherwise was around 120 dollars, but not nearly the same quality as the Optima. The Optima red top wasn't much more than that on Amazon, but I went yellow because it is an even better battery.Both the red and yellow are great though - WAAAAY better than other batteries. But most people know that about Optima batteries. I don't think they need people to endorse them.I'm writing this not so much because of Optima's quality (already known), but more so 2000 Mustang owners know that they can get this and be happy.It should be the same for any 99-04 mustang, the red or yellow top. But my knowledge is first hand for the 2000, and the Optima Yellow top Optima Battery that I'm rating: Optima Batteries 8014-045 D34/78 Yellow Top Dual Purpose Battery