In the old days, when most head castings weren't overly good or well developed as standard, say those designed pre the early eighties, (roughly). The old Stage 1/2/3 thing used to mean more. As pretty much all production heads off non exotic cars responded to the same things; three angle seats, tidied up ports, stronger valve springs, etc all the way through to really opened up ports, bigger valves, re-shaped combustion chambers etc.
Though the detail of sizes, and what material needed to come off from where, would change, all were much of a muchness.
Engine design has moved on vastly though. By the end of the eighties, we had a production engine in the shape of the XE with around 150 bhp as standard, that could with the right mods be taken to nearly 250 WITHOUT head work as we previously knew it.
Indeed, some popular engines now, actually have almost too large ports as standard. Others have long since had three angle seats.
So while it's still possible to modify them for different levels of performance, there's no typical magic formula anymore, and the "stage" approach to naming mods has got very vague and variable engine to engine.
Though ironically, Pinto's are one of the old generation engines, where you would, back in the seventies, early eighties, know pretty much what you were getting!