Stock heads/rotating assembly, hot cam/vlave springs- how far can you go?
Crate engine companies work within some fairly restrictive parameters. The end result has to satisfy the customer, while making the company a decent enough profit to cover all their costs involved and make money on top of that. So, you can bet there is room for improvement. I'll use Blueprint, for example. None of their engines come with any type of solid lifter camshaft. We all know which can make more power, everything else equal. They do that, ultimately to cut down on errors the customer might make and to help assure a good, successful installation and engine break in and good, dependable service. Lets face, it a hydraulic cam engine has room for fewer things to go wrong, since valve adjustment is generally not done except after initial break in and all of Blueprint's engines are pre-run, so all of that has already been done.
That being said, as I've said a lot before, "whatever" engine you build will have some power somewhere left on the table. That's just "how it is". To me the question would be can you come up with a better all around package, including dollar spent, verses value and reliability. Maybe......maybe not. It all depends on "how good" the crate engine company is. IMO, Blueprint is now probably one of the best.