the 750 have larger more protruding annular ring in the primary venturis than the 800 do, look down in one and see if is bulging alot or not much at all, you really almost need to see one of the 750 and one of the 800 to see the difference, but you just can tell by looking, second nature, heh
most of the 800 are on really old models and oldsmobiles and such
to set/check floar level you want to hold down the hinge pin that the float pivots on and is held into bowl casting with, and push down on the float end where the main needle is, make sure the hinge pin stays down
now measure with that white right angle measring thing in the carb kit,
to do this you put the end of the measuring thing on toop side of the float about 3/16" back from the very end of the float and measure from toop of float up to top of bowl casting where the gasket sits on
you want somewhere around 3/8" measurement
good luck