I guess I'll use this thread for a 'how I done did it in several less then easy lessons' (and usually with gooder grammar).

Got the car up on jack stands and it looks like the best place to mount an Odyssey/XS Power 680 size battery will be in their box and mounted on a supplemental cross member that I installed just in front of the gas tank. I looked at mounting it on the RHS frame rail, but on the inside, it will be within an inch or so of the tailpipe, on the outside, out of room due to the tranny cooler. It amazes me that everything operated with that part of my wiring - not pretty I guess I just ran out or inspiration about that time in the build.