gt40 heads

Well I have another question for these heads. I have just gotten the topend for a 93 cobra (intake heads and rockers, I have an ecam) for 150 bucks from a buddy! now I wana get more from the combo, I was gonna port the heads myself, then have them cleaned up milled and a good valve job and new springs. My next question is though would it be worth upgrading the valves to a 1.90 and 1.6 or just keep the stock ones? the stock ones are smaller so wouldnt that create more velocity? thats better for the street right?what do you guys think? I know that I could get a better setup but I wana look stock this setup is for a 93 cobra and I didnt wanna touch the original stuff bc its getting harder to find nos parts for the car but I do want more power from the car so I figured that this would be the best way. Thanks alot in advance looking forward to your ideas

thanks thumper I did read on the site and it made sense that the smaller valves actually helped out with velocity which should help out down low correct? I have set of performer heads that were ported by tony mamo from afr heads. he had ported another set of heads the same ones but with 2.02 and 1.6 valves and he said that mine actually outflowed the larger heads (mine were 1.9 and 1.6). so i was wondering if the gt40s would be the same considering they are smaller heads. I would like to keep the car stock but as you guys know is hard to do. especially now that I have a 347 in it and my 94 has a charger on it lol.