just rebuilt runs bad

if it was my problem, i would start all over, by first,pulling the chain cover and verify the timing marks on the chain sprockets are looking exactly eye to eye. second, i would make sure i hadnt lost a cam lobe.third,check all your pushrods and valves,then i would button it all back up and rewire the entire ignition system with a factory electronic set-up making sure everything is set up to start on TDC.fourth,i would verify i have 5-7 psi fuel pressure and a good carburetor, non necessarily new, but good. this engine should start and run without any issues under this set-up. if it does not , then i would be looking at changing the cam and starting over again. TDC ,rotor on #1, plug wire on #1,correct rotation on cap,correct firing order, ballast resistor terminal plugs in their correct spot. 12 v and a GOOD ground,is your engine GROUNDED? good fuel pressure and good carb. what else is there to it ?a good factory electronic set up is the way to go.i have built MANY big block and small block engines and i have NEVER had a problem getting them to start and run right out of the box on the first 1-5 cranks on the starter. once it is running ,twist the distributor and find where it wants to run and then throw a light on it and go from there.i just dont see what the problem is.it has got to be somewhere in your ignition system, unless you had a guy that builds nothing but 350s all day,but even then ,its not that hard to stab a cam and get it timed, and make it run. my $0.02