Yeah I'll organize things a bit better and add onto the DIY.
IT'S ALIVE! Car fired up on the PC680, no fires started, etc. I still need to protect the battery terminals a bit with electric tape for now, and then reassemble the interior of the car, which is mostly on my garage floor right now.
Later I'm going to go hunt down a good car audio shop that fabricates trunkish things, and see if they can mold me up a little plastic/fiberglass/whatever protective cover for the battery area, and then see about making the rest of the trunk usable with some carpeting or whatever.
For now, more pics:
Battery/trunk-area pics, all hooked up. Used those same little blocky connectors pictured earlier for all ends of the cable. At the battery, they're screwed to the little copper 90 degree terminals that came with the battery:
This is the engine-bay side, where I came through the little hole I made and hooked up to the big red inline fuse thingy:
This is a view of the passenger footwell with everything still removed. You can see my cable dissappear into some sound deadening material there, the 1" hole is behind that material (I held it back to drill, may have torn it up a bit in the process but it will mash back down and work fine).
