[Mis B]

I'm not sure if I understand your question about the part number on 840 and 291 heads. The only numbers for the heads that I have seen is the casting numbers: 3919840 and 3964291. 840 heads are square ports while 291 heads are oval ports. Jerry MacNeish states that 291 heads may have been installed on late model 69 Camaros but none have been found to substantial that. Our 69 Berger is a late May car and has original 840 heads. The original engine block has a Feb casting date.
Hope that helps.