On the guides its kind of a catch 22 deal, shorter guides will give you more flow however shorter guides won't last quite as long either, full lenght guides give more valve support against side loads. I think the replacement guides may also be a little bit longer than stock guides were but I haven't measured them in a quite awhile so you might check that out. If you were wanting to go with the shortened the guides don't have them drive the guides down as far into the valve pocket any farther than stock the excess can be cut off at the valve spring seat easier than trying to shorten or shape them in the valve pocket. With the shaft rocker arm assemblely that the 200's and other Ford small six engines have as well your going with the Yella Terella 1.65 roller rockers there shouldn't be as much side loading to the valve guides to cause any extra wear. The compromise position would be to use the full lenght valve guides or even longer than stock and then tapering them in the valve pocket so as to gain as much flow as possible that way. As to the spiral or plain the sprial might allow a little more oil in to lube the guides that can possibly help the longer lasting idea. Are you going to use a PC type valve guide seals?
Yes by all means on grinding out the exhaust port bumps I will always grind them out on any of the A.I.R. Heads and on some engines this can make quite a differance in port flow. As far as grinding around the spark plug I don't bother that area at all this could affect your swirl I only would polish the existing shape along with the rest of the chamber. With the stock size valves I don't see you needing to much unshouding the valves either. If you do unshoud the valves don't use the head gasket opening its 3.820 way to big the stock bore on a 200 is 3.680 thus would create a ledge that would cause turbulence. So scribe the blocks bore size around the heads combustion chamber and see what you have and for sure don't go out past that scribe line so the chamber isn’t any bigger then the bore size around the valves you are unshording, prorbally better is to keep most of the chamber smaller than the bore size, plus the more you grind on the chambers your add to your CC’s and loosing some of your compression.
You Distribitor is a 1968 duel advance with a duel vacuum advance canister these are the best of the older point distributors plus yours has a Protronix Ignitor so its not a bad set up if the center shaft bushings are still in good shape they can be rebuilt and recurved too. Best of luck
