maybe the guy you bought it from meant that the 4.3 is just a 350 missing a couple of the middle cylinders..and, as for your response to BillK- there tends to be a lot of sarcasm around here, and you need to roll with it. if you get defensive and otherwise overreact everytime someone says something you think is a personal attack, you will get ridden by a lot of guys- and ridden hard. you need to remember this is a camaro site-which is(was) built by chevrolet, so if you say stuff like"my 318 will beat your 350 with one spark plug wire disconnected", people might not want to help you out.this is the single best place on the net for automotive help, or just to shoot the breeze.but if you have an attitude, you aint welcome here, and will be put in your place.
as for your problem, i'd say to put the timing at about 10 degrees advanced, turn the idle screws 1.5 turns out, and start tuning. i would also look for vacuum leaks and simple things like that.if you need more help, feel free to ask the people here, but don't have an attitude.i can't stress that enough. we are here to help, and thrive on helping others, even mopar guys.
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16" IROC wheels