Edelbrock La Performer RPM Heads

I thought the 65cc RPMs were open chamber? Was there a 65cc closed chamber Edelbrock head available at some point with a part number of 6077? I know the current 65cc heads have 6017 on the side. I think the 6077 bare casting is 65cc but the complete head is 63cc after Edelbrock goes through it. I am not an expert tho.