Good morning, Stevco;
You are correct in thinking that the first line of defense with lens flare is a good close fitting lens hood. You can use any of the normal lens hoods that will screw into a 55mm diameter by 0.75 mm thread pitch filter ring. I have a couple of folding rubber ones by the Hama people that I like to use with mine. The lens hoods that I have from Minolta are a slip-on mount that secure with a threaded screw that clamps from the side of the mounting ring. Yes, they are more expensive.
I do have a few samples of the ROKKOR 1:1.4 f=58mm lenses, beginning with an early AUTO ROKKOR-PF and going to the MC ROKKOR-PF. They were made from 1961 to 1973. Minolta changed to the MC ROKKOR PG 1:1.4 f=50mm in 1973. Minolta was one of the earliest companies to use multicoating on their lenses beginning in the late 1950's. They continually developed their coating process and implemented changes and updating to that process when they believed that they had something better. They did not wait until a "model change" or a "model year end" to improve the coating process. Yes, the coatings on the later MD series lenses are even better than the ones on the MC series lenses. However, the main defense is still keeping the sun and other bright lights off the front of the lens.
Regarding the SIGMA or any other brand UV filter, including B+W and Heliopan, if you are doing critical work, and there is no danger to the lens, do not use the filter on the front of the lens. It is another glass element in the optical path with two more lens surfaces for reflections. However, if you are in an atmosphere that may not be safe for the lens surfaces (blowing sand, smoke, vapors, rain, et cetera) then leaving a UV or Skylight filter on the front of the lens may be prudent. Many of the better filters are also multicoated, such as the Hoya HMC series, for example. For most of the photographs we may be taking, the UV or Skylight filter will make no noticeable difference in the print if you keep direct light off its surface just as you would with the front element of the lens. Again, flare control is still important, and the use of a lens hood (filter hood?) is still a very good idea.
One justification I can offer for a metallic lens hood is the ability to absorb much of the shock if you drop the camera. I have had to replace a hood that gave its all in saving the lens and body from damage. I do not know if the folding rubber lens hoods can offer similar protection under all circumstances.