[Christ]

I wouldn't really be comfortable with a constant engine temp much over 225*F.

If the fan is kicking on, it's draining MPG - keep it from kicking on, and you might even get another mippig out of your engine. (Electrical load on the alternator. Even if you're running w/o alt, it's taking juice away from your other engine components from the battery, which only has so much current to supply, and usually not enough.)

For both of you, I suggest deep cycle batteries, volt meters, and alt kill switches. Don't replace your original battery right away, but if you need a battery for ANYTHING, it's a good excuse to get a deep cycle for your car, and put your current battery in whatever needs one.

I also have to suggest LED lighting options, and "lightening the load", electrically speaking. If either of you have DRL, ground your parking brake wire to stop it from coming on during the day, or if you're good at wiring, rewire the circuit into LED's instead of the high-beam lights.

I believe your headlights are 55W low and 75W high... consider some driving lights that are around 30W for when you don't need much light, like just after dusk.

I'm not sure what to do for any serious gains in weight reduction for your cars, so no advice there. I do know that the 1.9 1st/2nd gen engine fits your Zetec transmission, as well as other (longer geared) transmissions fitting on your Zetec blocks, which might help.

Since the 1.9 block will fit, that means the 1.6 block will also fit. You can go smaller, as long as it's something you're comfortable with. You'll need to modify several things to get either engine to pass emissions inspections, though, since you're both OBD-II compliant. You'll need to make sure that all of your current emissions equipment is installed on the new engine, and that your ECU is reprogrammed (with a CARB compliant tune) to run the smaller displacement.