[v8volvo]

Others may disagree but if the cars were running 2 years ago the fuel probably will be OK as long as it doesn't have water in it. Diesel doesn't turn into jello like gas does and can have a long shelf life if it is not exposed to air or water. If the tanks are reasonably full and the fill caps were on, I doubt you will have an issue running the fuel that is in them. If the tanks have been open or there's very little fuel in them then all bets are off though.

Be prepared to check the fuel filter water separator for water a few times, and to replace the filters after the first tank or two since any scale or rust that built up while the cars sat will end up there.

YMMV but I have gotten a few going after sitting for years and they all drove home on whatever was in the tank.

$250 is a deal for a rebuilt head if it was done decently well, go for it, or if you don't want it, others here will. Other spares that are good to pick up if you have a source: fuel injection pipes, injection pumps, vacuum pump, cooling system components/radiators/hoses, power steering pump bracket, alternator bracket with radiator fan bearing, starter, engine wiring harness and battery cables if in good condition, glow plug relay, any and all engine tools. All of these are common needs and hard to find, good to get them if you can and if you don't use them, you'll be able to find homes for them. If you are offered other items, feel free to ask here.