Oil pump and timing chain questions

Yes, use a gasket on the oil pump. It won't blow out. Mancini racing sells gaskets for them single for $6. You can also make one yourself with gasket paper.

Timing chain. Align the marks with the cam at 6 O'clock and the crank at 12 o'clock, the crank keyway should be slightly on the right of the marks at about a 30° angle. I find the easiest way to to that is to install the chain and gears together and line up the marks using a thin screwdriver or sideways ruler going through the center of the gears and then line up the marks to it. Then turn the crank and cam to where you can get the chain and gears on without disturbing your setting. You may have to turn the cam and or crank to do this. Then after the chain and gears are installed, verify the marks again. Remember to use a straight edge and pass it through the center of the cam and crank bolts, and then look for the marks to align up at 12 o'clock on the crank gear and 6 o'clock on the cam gear. The crank keyway should be about 30° to the left of the crank gear mark at 12 o'clock.