[COPO]

The #291 are most definitely square port heads. They are on the '70 LS-6 and the '70 L-78. I believe you may be thinking of the #290 which are oval ports. I have not seen a '69 w/#291 heads, but the info in CBTN says they ceased production in May of '69 on the 840's, so any solid lifter BB built after the existing stock was gone would have had the #291 heads. I can tell you the #840's are much easier to find.