I have a set of 360 heads pulled them off a running engine and from what I could tell this was the first time it has been apart. The heads have different cating numbers one is 3769974 the other is 4027569. Does this really matter if they are both 360 heads. Or do I need to have a matching set they both look the same to me. I just wanna be sure before i rebuild them if it would matter. Or if they are the same just made different years.

 

Well they both are indeed 360's. the 3 series ones were produced in 75 & 76 and have 1.80 and 1.60 valves and the 4 series head was produced from 77 to 86 and have the same valve combination. Other than that its your call bro.