I decided a while ago I wanted to re-locate my battery to the trunk to clean up the engine compartment as well as help with weight distribution. Since I don't have a spare tire anymore with the C4 chassis conversion I figured the spare tire well would be as good a location as any so I researched battery sizes to see if there was a standard size that would fit in there. I found a few that would work but not any that would have enough cca amps without spending a small fortune on a lithium battery. I also wanted a battery that was available in an AGM type so venting would not be an issue. So what I decided to use that was close to fitting and would be easy to get anywhere in an AGM type is a group 48 size. My 2007 Sierra used this size as well as our 2009 Cadillac CTS.
So I made up a cardboard mock up of a group 48 size battery to see how it would fit knowing the spare tire well would need to be modified.




As you can tell it sits up way to high as is.
So I decided to go for it and remove the spare tire well to widen it out to fit the battery.




So after drill out about 40 spot welds I got it out to make it easier to work on.


A couple of temporary braces tacked on and sliced down the middle with pie cuts at the ends to widen it out enough to fit the battery.


Center filler piece #1 fitted up and tacked in place. Throughout the process I screwed the spare tire well back in place to make sure it would still fit in the end.


Back out and tacked up a little better.


Back in place to check how the battery fits. Should work good now.


Another filler strip fit up ready to tack in. The Gorilla tape works great to hold odd shaped things in place when a conventional clamp won't work.


Another view.




All tacked up ready for lots more welding and grinding.
Next up will be to make the battery tray for the tire well.
Brian