In addition to Brian’s sound advice, I would suggest that you look at the catalogue of a UK supplier of ignition parts, “Independent Ignition Supplies”,
Among other things, they specialize in platinum points (quite expensive), which can replace the original tungsten(?) points in the Miller distributor. The original contact breakers must be used, but new points can be screwed or riveted on.
I have never dealt with the firm, but their catalogue looks interesting.