Gitzo seems to change their model numbers as the mood hits them. Originally they used names, that confused all the camera store clerks. If you didn't do high volume you were lost. Then, a combination name/number, finally numbers, Now numbers are primary but they still have names......
Anyway, The 300(Studex) series is more than adequate,Largest leg diameter of 1 1/8" for any medium format and most cameras including light 5X7's
400(Interpro Studex) are basically the same legs but with a much larger spider and the ability to use rapid,crank, or no center column.
500(Studex)Larger leg diameter @ 1 3/8". Strong like bull! Fookin' heavy, Good for just about anything, over kill for a Minox.
My only Gitzo right now is a Studex Giant 9'+ and really FOOKIN' HEAVY