No valve stem seals?

[VintageMusclecar]

Assuming these are a set of OE type heads destined for street use, leaving out the seals is a bad idea. Some shops will omit the seals just on the exhaust side since it doesn't see much vacuum, but given the proper clearances (dependent on valve and guide materials being used), there is absolutely no reason not to install them during a street rebuild. Leaving them out is all but guaranteeing excessive oil consumption, not to mention plenty of exhaust smoke.

As far as dedicated "racing" heads, while some may not see anything wrong with leaving the seals out, they aren't taking into account that excessive oil contamination in the chambers drastically increases the probability of detonation.

My $.02: have a set of seals installed.