If you could bring only a few things before you drove 400+ miles

[slammin.e28]

Bring a spare timing belt in case it breaks on the way.

[E30Gus]

Beef Jerky and clean undies!

[lambo]

a pipe, an 1/8th and maybe a 12 pack in a cooler for when your waiting for the tow truck. No matter what you bring, you will not have the correct thing for what you need.

Seriously. We limped an E30 with a shit cooing system 600 miles back to Colorado through New Mexico.

I would vote on Triple A and coolant hoses/water.