Help me understand rebuild vs crate?

yes knowledge is power . You said new LAX heads for $1500 you might find they need a little massaging and that costs money , special tools cost money , you are probably going to find you have way underestimated the true cost of building it yourself with gaskets etc...and that $1000 savings doesn't exist .I would buy as complete as you can afford because the builder has a better supply cost than you and will add all sorts of bolt ons needed to be complete at a much better cost than you can buy them just to get your business . I bought my stroker complete from carb to pan , water pump back to distributor and saved a ton of cash on those 4 things plus everything tied to them .