I installed a braided ground strap between the back of the engine and the firewall ground block. This is the heavy-duty conductor that carries the hundreds of amps of starting current back to the negative terminal of the battery. It's fastened at both ends by adel clamps, so there's no strain on the actual terminal ends.
Closeup of the attachment to the engine… it's secured to one of the auxiliary alternator mounting studs with a nut and lockwasher, and is clamped to a neighboring stud.
Then, because I have equal love for both belt and suspenders, I installed a second one. If the first one were to somehow come off, the full current of the starter would flow back to the negative battery terminal through all the various sensor wires, control cables, etc… quickly turning them into smoke. Thus, a backup ground strap. This one goes between a sump bolt on the left side of the engine, over to a nutplate on the lower firewall. I couldn't find a way to provide strain relief for the ends, but it's only a backup.
There's so much stuff back there that it's hard to get a good picture, but you can sort of see where I put some heatshrink tubing over the second strap. There's no danger of a ground wire shorting to ground, obviously, but I wanted to guard against it accidentally rubbing against the engine mount. It doesn't touch it currently, but it's possible that it might flop around and tear up the powder coat.
