OK so you have a 68 stand alone (non lean burn) carb & a good vac adv dist. other than the std tune up issues: compression check/no vac leaks/ballpark timing/good plugs/wires etc as you said you might order some bigger jets & good point the guy mentioned that Holly jets are stamped on the side (at least the ones in my white plastic holley jet box are). Oreillys is pretty good about ordering run of the mill speed parts & could probably get some jets in for you. Not sure which company sells them individually but I've seen em. You might get a 40-50-60 & do some experimenting. Holler how things go