I wanted my batt under the hood and not in the cab but also wanted to keep it away from header heat. Final solution was making a box (sad photo) that mounted to the fender on the outbound side and mounted to the frame on the inbound side.
Mine is in one of the those plastic battery boxes behind the passenger seat. Came that way when I bought it 20 some odd years ago and it's worked out fairly well.
I think the only reason the PO located it there to begin with is because of the fibreglass flip front clip, which has has no inner fenders to mount anything off of.
The engine is a Chevrolet 350 cu.in. crate motor rated at 290HP before the Edelbrock add-ons. I used the Marks V8 adaptor kit which allowed me to use the stock Toyota T-case and transmission. One of the benefits of this kit is the driveshaft lengths are stock and unaltered.