battery relocation spots for 69 stepside

[Dagobah]

Howdy errbody. I am looking to relocate the battery on my 1969 GMC stepside. Also, it is a short bed. The goal is to move weight off of the front end, so anything behind the front wheels would be an improvement.

Originally I thought about mounting it to the firewall. I don't see a lot of people doing that. I've also seen them mounted inside the cab behind the seat. I'm not sure about that. I don't know if sealed batteries have to be vented.

Ideally, it'd be down low and between the front and rear wheels with reasonably easy access. I see people mounting them to their frames, but I think that's always on fleetsides. Your suggestions are much appreciated.