Thanks to derHusker, for posting this video. This is the closest thing I have ever seen to what I learned about Santa Maria BBQ back in the late 1970's.
The True Story of Santa Maria Style BBQ.mov - YouTube
I learned from some old men, whose time on the pits dated back to the late 1920's and this is pretty close to what they told me. If you can find Top Block, it is worth the cook. DO NOT COOK IT LIKE A STEAK. It is cooked on rotisseries, above a moderate oak fire, and it will take 2 hours or so to get it to 140F internal, low heat cooking.
By the time I was learning, these guys had adapted to smaller pits, and used racks, but, they did not grill the meats as we are all lead to believe, They did Top Block, Ball Tip and Tri-tip, over a 'slow fire' and it took 1.5 to 2 hours to get it to medium (140F internal). Top Block with the lifter/cap in place on a rotisserie will trump tri-tip.
Also note, he calls it Live Oak, not Red Oak, the actual wood used is Coastal Live Oak not Red Oak. People from the Mid-Atlantic called it Red Oak back in the 1950's when they first came out and saw the trees. They are related, but, we actually used Coastal Live Oak out here.
This tradition actually dates back to the Spanish ranchos, and the tradition of harvest and spring festivals they brought from Europe. The specific purpose of the original Santa Maria BBQ was a party to celebrate the end of the cattle drives and harvest. Traditionally, cattle were harvested in late fall, after fattening all summer and early fall. The vaqueros and caballeros would be in town, and the ranchers and land owners would sponsor the harvest festival as thanks to their workers.