I just had a discussion with the fellow that rebuilt the motor for my L72 '69. His recommendation for my needs (available at NAPA stores and not for use in catalytic equipped vehicles) is Valvoline Racing "Not Street Legal" 20w-50.
http://www.valvoline.com/pages/produ...asp?Product=94
ps - The engine dynoed at 519hp @ 6100rpm and 493fpt @ 4600 rpm
