For the less involved types.... use perma tack to hold the gaskets, glue them to the head ...and walk away. Don't bother sticking them on the intake and matching it the same, chance is it won't line up and you'll have just created ledge when the manifold goes to one end or the other, a ledge on the wrong side.
Fkr the more involved types, do this.... use the plastic locators to hold the gasket in place 'felpro has them', put it together dry, drill with a tiny bit through the flat of the intake flange next to all 4 end runners just till it goes into the head 1/8....then take it apart, dye around the ports ,use the drill bit/s to locate the gasket, tape it if ya want as well...then scribe and grind. Do the same with the intake...then assemble and locate with the drill bits in each corner hole, tighten...done. It's lined up for real.
ps, when I did a lot of 318 heads...after working them to 210 cfm with a stock 1.78 valve...opening the port window to a 360 size was only worth about 4-6 cfm on the intake side. Don't do it on the exhaust or you'll hurt flow.