timing issues

could someone help me? I put a 1980 350 in a 92 truck i pulled the distributer out and now put it back in I am pretty sure it is lined up but it is missing a little on low rpm and take off. It also has a knocking sound whien i first roll the moter over. Could someone please tell me what i am doing wrong?

Before you pulled the distributor was it running fine? How long was the engine not running before you put it in the truck and were there any mods that you put on the 350?