L43 Head

[luis93436]

2001 sonoma 2.2 L43

Hello today is sunday and the dealer is close I hope some one can help me:

while swaping an engine I noticed that there are two different types of heads for the 2.2 liter sonoma.Both engines look the same but I notice the gasket for the exhaust manifold is not the same, then I look at the head just to see some differences between the two,( I never bother to check when I bought this used one) one is the flex other the regular (i think) I was going to only swap the exhaust manifold by I am afraid is not going to work should I change the head to? are the blocks the same? any ideas?