Apart from stuff you can find on distributors in the FAQ and elsewhere here and on other sites using a search, our 240 gurus will be able to give you far better guidance on distributor issues. A good idea to start that discussion in a new thread specifically seeking advice on worn distributors.

Many of us would say the single most important part to have is a spare fuel pump relay (failing that, at least carry a jumper wire or paper clip and instructions on how to bypass the 240 FP relay at the fuse panel). In the electrical department, next thing to grab would be a spare AMM (as you have done) -do remember that unplugging a bad AMM will often get you started and able to limp home. Everything after that is pretty much personal preference and knowing what's gone or showing early warning signs. For me, electrical stuff I would want to keep an eye out for would be a bargain bulb sensor relay, ignition amplifier, alternator, coil, decent distributor, maybe an ECU (except your LH2.2 ECU is much more reliable than the early LH2.4s). If you're going to keep your Volvo forever, it's hard to imagine not wanting spares of everything electrical when the price is right.

Actually, when cruising 240s in yards, the stuff I was always on the lookout for were things like undamaged door pockets, good front seats, floor mats, door/tailgate hinges, taillight lenses, clear headlights, wheel covers, nice rims, radio antenna, radios, door panels, other bits of trim, ... -stuff that is no longer avail new or hard to find, especially in good condition.

I'm sure others will have all kinds of suggestions of what to grab. When it comes to old volvos, indeed any old car, the only constraints are the size of your wallet, the amount of storage space you have and the willingness of your family to put up with it all.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now