if you check the classifieds you will see some one has the molds for sale for heads for the 6 and 4.
the problem is most people with a 6 are cheap. look at a lot of the postings, i dont have a lot of money to spend or i dont want to spend a lot of money. when told to send their heads to a good shop they take them to the local butcher shop and get a half ass job. some too cheap to even buy a shop manual to find out the tourk specs.
the 6 is either a work horse truck or a well put together proformance motor.
maybe with gas getting more expensive the 6 will make a come back.