SOVREN and whatever the vintage association in BC is called. In this case, the car is "vintage" rather than "historic," so the cut-off date is 1962, prepped to FIA GT 2-liter class. There are three levels of GT class, and this car is in the top one, so we get to do a few extra mods. They are allowing a B18 in a 444 on the basis that a 544 is really the same car, and would have come with one in '62.

In a nutshell:

Must use original type pistons and rods, .040-over max
Must use original head, but all porting and chamber mods are okay
Any compression ratio is okay, but must run on pump gas
Any cam is okay
Must use original type/size carbs on original manifold without adapters -- HIFs would be technically legal, but not really in the spirit of the thing
Carbs may be modified, manifold may be ported
Must use original exhaust manifold (and they're okay with the late B18 manifold with dual outlets, for some reason. I'm not arguing...)
Any exhaust that meets decibel limits
Any radiator, but must use the original mounting points
Body may not be modified in any way to let more air into or out of the engine bay -- no cold air box, louvers, ducting, etc.
No reference to flywheel or clutch, so (unlike in IT) those are free

There's a lot more, but that's about everything that pertains to making power.