I'm guessing you're running a TH350 transmission with nearly stock tire sizes. Of course it's a wild guess, since I have no other data to go on.
I'd say to go with the mild performance converter ~2000 advertised stall speed and 3.55 gears. You'll need the extra stall speed on your converter to compensate for your cam. I know it's probably advertised as the hottest cam you can use with a stock converter, but Chevelles are heavy cars and a little higher stall speed helps.
Of course, everyone is different. 3.73 gears will give you a bit more punch, but higher engine speed while cruising the highway. 4.11 gears are an absolute blast for driving around town, but aren't much good for highway cruising (although I've cruised the highways quite a bit with 'em in the past). People will definitely turn to look at you if you cruise the highway with 4.11's.
I highly recommend using a calculator to see what your RPM will be at a given speed. I use the one at Randy's
. It should give you a better idea of what you're looking at.
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