Used Engine?

Alright, so liek many other ppl on here I want to build up an A20 engine, now I only got two questions, one could prob be answered if I searched and that one is, What is an A20A4 whats the 4 stand for? and when in a junkyard what should I be watching out for on the engine which woudl say STAY AWAY!??

a20a4 is a different incarnation of the other a20 engines. i think it's basically an 88/89 a20a3 with 86/87 a20a3 manifolds and less emissions equipment.