[madden]

HI

can anyone tell me more about the following sbc heads

casting #340292 – 1970 replacement, angle plugs, 64cc chambers

1)are they rare?
2) were they a replacement head for the #3927186 head on the LT1 sbc? if not what were they a replacement for?
3) valve sizes?
4) and finally what are they worth reconditioned?

thanks so very much
chris