I don't understand how a starter or alternator would be affected. It's copper wire wrapped around with magnets, I can understand anything with a capacitor or circuit boards. The issue with modern cars would be the computer systems, anything late 90's and up probably won't run, mass airflow sensors, ignition modules, etc would pop, not letting them start. Early to mid 90's would have ignition modules which would be damaged and that would make them dead as a door nail. Effectively this, you would need something with our an ignition module, that would be the plan, I would say diesel would be the way to go, a early to late 70's diesel truck (1ton) would do it.
If there was to be a shtf auto, you need something that can be effective in all terrian, heavy to blow through road blocks, tall enough to be able to drive over prospective dead bodies with out getting stuck, and tough enough to with stand multiple blows to the front corners yet still able to maneuver after . This leads me to think a truck or suv in the late 70's early 80's with a plow on the front. Probably a v plow of sorts. Diesel for the added bonus of being able to run on just about everything, and the torque it has. Also the lack of crush points on the front end will keep it driving longer. I would say keep a pair of Tim snips and a crowbar, and some old school tire tubes with you, nothing worse then getting a flat and having to ditch a ride. If you have tubes your tire can be effectively damaged by you should still be able to drive a reasonable distance before it breaks down, I wouldn't suggest high speeds. With that being said a large truck, deuce + I don't think would be good, it would pin you in when things get too tight.
Just my 2 cents