[true blue 32 man]

I have had quite a few 32's over the years. On ones with the original engines and the 32 large plug heads ,I noticed that some have the part number cast into the head 18-6049 LH and the other side 18-6050 RH . Other large plug original heads are plain with no numbers. Is this a early/late production thing or are the plain heads service heads? Being that they were lower compression than 33's and later. I would think that few would be replaced and few would have been sold through the parts department as replacements. A few years ago I bought a straight down drain 32 engine but did not come with the correct heads. Just got it back from my engine man that freshened it and heard it rum on his engine stand. It has all correct externals , alum pan ,correct exhaust manifolds ,tall water pumps ,ect. It has plain heads I have another set of heads with the part numbers. Do i need to change the heads to be 100% correct? Hope some of you barners out there can shed some light on this Thanks Pete