Are you asking just about the engine or a complete restoration? For the engine, the rods all have numbers and I always phase them back in exactly how they came out. The numbers must match up as the rod and cap were machined together. Mains obviously have to go back in the right positions. I also mark my heads left and right--important if you have port matched, but not critical otherwise that I am aware of. Many people who re-use their valve train try to keep it all in order as well, I am in the habit of buying new. Lifters should be replaced unless rollers. Hmmm, what else....
If you are asking about the whole car restoration---that will be a longer list.
erg..............take photographs of everything before it comes apart. I can not stress this enough! Buy a paint marker or at the very least get a "magic marker".