1967 915 heads any good?

Yes, they are decent heads. If you have a mild engine now, they will add some compression at minimum, maybe add some flow depending on what else you have. In the past (prior to the cheaper aluminum designs) we used them a lot. In "stage 2" configuration (not maxed out) they'd make over 500hp with a mild solid cam (MP .528 ) on pump gas.
But like IQ is hinting at... now it's cheaper to get a better head if you are starting from scratch.