Help with casting numbers

[red65stang]

I got an engine from a friend today and im trying to find out what size it is. The emission sticker on the valve cover says its a 1974 302 but how can i be sure.
I did manage to get the casting numbers but everywhere i search i cant match my numbers to anything.

any ideas?

casting #s D90E-6015-E3A
or E
or B
I cant tell.