So I recently picked up a used (1987) HK M1 Super 90. It has an 18.5" cylinder bore barrel, no vent rib, not threaded for chokes, milled in front sight. Obviously those traits are less than ideal. Now I could spend $400 on an M2 barrel and handguard to make up for the length, rib, sights and chokes, or I could spend $200 to get it threaded for chokes, but then I wouldn't have the the vent rib or longer barrel. Would it be a reasonable option to sell the M1 and pick up an M3K and use the leftover cash to get it set up? Is there a big enough difference performance wise between the two platforms to justify the downfalls of my particular gun?