What were the conditions of the failure? Why did you take the engine apart this far? Why did you think it jumped time? Does the engine cranking sound unusual? Does it sound like it has no compression? I really want to know what happened to this truck to make you think it had jumped time.
To answer your questions, when you have the timing set installed, the marks on the crank gear and cam gear should be aligned vertically (perpendicular to the ground), nearest one another if I remember correctly. You should check a repair manual to verify. Haynes should have clear photos to illustrate this. Once this is accomplished, cylinder #1 will be at top dead center of the power stroke. Your distributor needs to be installed with the rotor pointing at the cylinder #1 TOWER ON THE DISTRIBUTOR CAP. On most, if not all, Chevy V6 and V8 engines, this does turn out to be pointing at cylinder #1 on the engine (right front corner). Make sure when you install the distributor that the oil pump drive on the pump and the distributor line up and the distributor goes in all the way. Failure to do so could strip out the helical gears on the distributor shaft and the camshaft. Getting that distributor to drop correctly is sort of an art form and can really trip up a novice, but don’t lose your patience with it and do it wrong or you will never get this engine running. Once the distributor is correctly installed, you can try to start the engine and set the timing. Your truck has electronic advance which needs to be unhooked before you can set your timing. Check your repair manual for the procedure. If it doesn’t start, you need to start diagnosing the problem. For a no spark situation on this vehicle, I would suspect the ignition module. It is located under your distributor cap and is easy to replace. Good luck.