I carry about every spare I have except the spare motor, I carry gaskets plugs ,oil trans fluid, flex plate,starters, alternator, transmission, torque converter, battery, battery cables,control cables,spare pilot chute,spare fuel pump, rod ends,spare fuel tank cap,AN hardware. Rocker arms , pushrods, valve springs, oil filter,spare alternator,air pump anf fuel pump belts. I also carry thee different kinds of epoxy, silicone, sealers, thread lockers etc.
I usually race >100 mi. From home and usually two days so I try to bring any thing, tools and parts, that I can to assure that a minor problem could not end my weekend .
The way I look at it spares are of little use back home in the garage.
I don't bring the spare motor because I would also need to bring a porta crane too and together they would add close to 1000# to the trailer and there is only so much stuff you can fit in a 32' trailer that already has a dragster, a jr. Dragster and a golf cart in it.
(If I had the room and enough generator I would carry a small TIG welder but alas 3000 watts is just not enough juice to support one.)