i need help identifing merc heads

i have what i think to merc 410 heads. the casting numbers make no sense. they read, 6090E and RDC between the two center ports. where the date code is it reads 87K. i really need to know what they are off of.
thanks Lucas

 

6090 is the FoMoCo nomenclature for a cylinder head (group number)....you'll find it on Y heads, FEs, six cylinder heads...etc. Doesn't mean anything other than that the part IS a cylinder head.

Need a little more information. Did you check the underside of the heads?

 

i did check everywhere i listed all the numbers that are on the heads.

 

The RDC is likely actually EDC. If so, those are early FE heads, like 1958-1959 or so.

Do they have a frost plug on the end?

 

there are no frost plugs on the heads