Every aftermarket aluminum cylinder head will outflow these all day long. One of the magazines did a head to head test and the heads today are head and shoulders above these. (notice all the head related puns in there!?!?)
I think they are cool and would run them if I owned them. I have tried to buy some sets but the rocker stud bosses are usually cracked or the chamber is beat to death with a broken valve. Tricky part is you need a piston that will work with the closed chambers and not hit. Not too many closed chamber pistons being made anymore either.
They are probably worth a lot if they are '67 - '68 dates but the later they get the less collector value they have. I bet you could get $1000 for them, maybe more.