all a12 are round port
all a12gx are oval port
all a15 are oval
a14's can be either round or oval but generally are oval
a14gx are all oval

only way there could be an exception is if there was after market porting done to make it so

all oval ports also use a diffrent inlet manifold stud pattern to all round ports (again unless studs have been added), round ports have a single stud between two inlet ports at the top, oval ports have one stud outside each port at the top

gx heads have double valve springs which you will be able to see if the rocker covers off

there is identification numbers, but again these are under the rocker cover

all exhaust ports and manifold studs are the same

then there is water jackets, and im not gonna try remember off my head which ones do and dont have those