There are several shops that can port heads. I have used Xtreme cylinder heads for this work. They CNC machine all the ports so they are the same. They can offer larger valves and even make their own heads.

As for Cams, below are some commonly referenced venders. They all have cam versions that are more modern grinds than factory:

DRC, https://www.drcamshafts.com/911profiles.htm
Webcam, https://www.webcamshafts.com/
Elgin, https://elgincams.com/porsche911/

All of the above have some very similar spec cams.

Some other shops have their own proprietary grinds.
https://performancedevelopments.com/
KNIGHTRACE (search this user name on forum)

I have found the MOD S cams to be a nice upgrade with good torque and power on 2.5-2.7 engines I have built.

I would discuss your goals with some of the shops/venders and see who you are comfortable with.

John

Best cam for 2.5 is Mod-Solex