Adding a second battery

I'm looking for a way to add a second battery for use with a camper on my 88 F250 351W. I prefer to put it under the hood for ease of maintenance but I don't see much room for it. There's a good place for it on the left side but the radiator overflow tank is there. Is there a kit available that relocates the tank and provides a battery tray or was there a factory option and would the junk yard be my best source?

you have to use a battery isolator, the ford system doesnt always do so well with two batteries, its safer that way anyways, both will charge but only one will run the truck leaving the other for the camper

I will be using a large relay to isolate the second battery. I don't have any problem with the electrical side of the installation, I've installed and used diode isolators and relay isolators on other trucks but they had plenty of extra space. I just need to find a place to put the battery, where to relocate the parts that have to be moved, and a source for the hardware.
I checked a couple of junk yards and had no luck finding parts that would work in my truck. I guess I'll try the Ford dealer next but I doubt if they have anything for an 88.

Hey Torqued

I have had a few F250's and isn't there enough room near the firewall passenger side? It's been a couple years and I wish I had a picture.
You may need to make a bracket to mount it, but if not the wrecker is still your best choice again.
When you find one make sure you fill the old one to the cold level and pour it into the new one and mark it, same with the hot level. The volume markings must match.
If you can't find one you could always make one out of stainless and have a pyrex or clear tube for a level indicator. There's a custom project! ;)
BTW
When you do relocate, make sure to use a new overflow hose and clamp both ends, it has to be a sealed system.

Most of the space on the passenger side near the firewall is taken up by the AC. This may end up being a custom fit. Another possibility is mounting the battery in the camper. There is space but it would have to be a sealed battery due to lack of ventilation. I prefer an under the hood arrangement. Another trip to a wrecking yard today didn't help. The Ford dealer's computer was sketchy about a second battery in a gas F250. It mentioned it but all the illustrations were for a diesel.
The overflow tank is a dual unit that includes the windshield wiper fluid tank also. So both would have to be relocated along with their hoses/wiring.