Recording Car Engines Question

[Gohanto]

I've got a chance to record some vintage cars in about 2 months (Ford Model-A and a couple others) and I'm looking for some help on a couple points.

From looking at various posts, my current plan is using my H4n on the interior running 2 SM58s (one taped above the exhaust with polar fleece on it, and the other taped under the hood away from the distro and spark plugs) through a SD MixPre and into the 1/4" DI inputs on the H4n. Then using a NTG-3 in a blimp to hang out the window for tire sounds and grabbing pass bys, stops, ect... Plus having spare cables and pads with me.

Q's
The line inputs on the H4n are unbalanced. I've read about the shock danger of the spark plugs and distro frying gear, but even when all the wires are placed away from the "danger area" it is that likely to be a noise problem since the signal isn't balanced?
Are there any wired lavs under $200 that would be worth getting for this? Seems hard to justify getting some of the nicer ones I've seen recommended if I'm only using them for car engines. (Though if that's the case I'll likely invest in some down the road, just don't have the money currently)

[Noiz2]

I've usually used dynamics under the hood. As long as you keep everything away from the high tension circuits you should be OK, that would be the spark plug wires and the thick wire running into the distributer. AND that means keeping the cables away also. And yes you might pick up RF clicks and pops. But you just have to adjust placement if that happens.

[SMuir]

Try to mount the exhaust mic to one side of the exhaust, out of the direct line of fire. Adding another SM-58, wrapped in pipe insulation and taped to the rear door panel, angled towards the back tire will give you a bit more of that "rubber meets road" sound.