This is the actual add i found, its a link to a collection of adds that has been posted up here before, the rest of them are quite interesting too.
1972 Victa 2-Stroke 125cc Impala Brochure Cover The blurb references the fact that it has a narrow chute (I'm guessing in compaison to the VC-160) maybe this has something to do with it, your second base is as far as i can tell, the same in shape as the green mustang you picked up, and the same catcher i would assume would fit both, is the rear of the first impala base anny smaller, would it need a smaller catcher.
I'm noticing the one in this add has the same indent around the victa badge, as your first one, i would hazzard a guess that your first one is the V126 1972-1973 4-Stroke Model, while the second one may well be the 73-74 V156 Model, the Mustang (which i beleve shares the base of your second one) came out for the first in the 73-74 lineup.
