On the subject of MK1 58 Patt ive always gone by Howletts book(not that keen on the Europa series of webbing books to be honest).
Regarding the ammo pouches ive always been led to believe that there were only 2 types,early that were smaller,straight belt hooks,reinforced larger top pouch sides and the strap and buckle arrangement inside the pouch,later pouch,larger,angled belt hooks etc etc.
Well,just got a couple of oddities-British issue(not foreign)CN numbers,dated 1965 by ME Co and exact as the early pattern other than the top flap sides arent reinforced and same size as the later pouches so seems that there were at least 3 types and not 2 as always believed.