You can get the AFR 165cc heads for about $100 less than the 185cc ones. I just thought that if you get the 185's you would save money farther down the line if you decided to do a stroker which sounds like you are interested in doing. Whatever you do dont do a stroker with a stock top end you will be very unhappy.
One thing to consider is that AFR's are the best. You can read about it anywhere. Sure you can port and polish the GT40 Y303 heads and you can upgrade the spings and retainers etc as well to make them comparable to the AFR's but now you just spent at least $400-$500 and now you just bought yourself AFR's.
Consider it this way, you get the GT40 Y heads and you will get a 40-50hp increase with a good cam and intake. You get the AFR's and you are looking at an 75-90 hp increase. Big difference in dollar per horsepower.
Before you start buying parts and convincing the wife I would call ed curtis. I cant stress this enough. Talk to someone that has done buildups millions of times and sells all the parts in question. You tell him your desires both in performance and driveability and your budget and then let him give you the skinny. If you would like even more diverse advice then go to
www.stangnet.com or
www.corral.net. These forums are full of people who have gone down the same road as you.
For torque at the low end it is all about port velocity. For the top end it is all about max flow. Some companies create heads that use huge ports and big valves to accomplish this. Others use big ports and small valves. And there is AFR which uses comparable average ports with average sized valves and much higher compression ratios due to smaller combustion chambers. They also create a perfectly blended and contoured intake and combustion and valve seat and angle. More importantly they create bigger than average exhaust ports with average exhaust valves to aid the very exhaust deficient breathing of the 302 motors.
AFR's do not flow the most air and dont use the biggest ports or the biggest valves. But they make the most max hp and tq and more importantly make the most average power and tq. This average is what makes you feel power all around the RPM band and makes driveability great as well as peak performance.
You get what you pay for most of the time. Sure some combos have great bang for the buck. For instance you can get your stock heads cnc ported with bigger valves from Powerheads in Fullerton CA. They will flow air and make similar power to the GT40 Y303 heads. They also upgrade the valvetrain on the heads to accomodate your cam.
Be careful not to buy the biggest heads with the nastiest cam and massive demon carbs. You have no idea how many people have the slowest performers, worst idling, worst gas mileage, bucking 5.0's out there. Some combos just work together. Buying the biggest and best of everything is usually the worst way to go and the most costly. It is all about the overall combo, heads/cam/intake/carb/exhaust/gears etc. When you talk to ed curtis you should tell him about your current motor and exhaust and everything else that we have discussed earlier. He has given me great advise before and it was actually steering me away from buying something from him so you know he will be honest.
If you have to notch the pistons then get them notched. If you have a tight budget then save up more money and do it right. Being ansty and quick to buy what you dont really want or need will cost much more than just being patient and doing it right. If you dont want or need 400 hp then dont worry about it and look for a setup that ed curtis put together or suggests to get you there. He may tell you to just have your heads ported and polished etc, and then put an off the shelf dual pattern cam or even a ford racing cam or even just some 1.72 RR's and advancing your stock cam a few degrees. You never know how it will end up until you brainstorm and write down your goals for the car and then put them together with your budget and timeline. Then when you have made your compromises and decided on your priorities you go find the parts to meet your needs and put it together and fire it up and enjoy knowing that this combo was the right one for you and not somebody elses dream that your driving and hating the whole time.
I am sorry for the long posts but I just want to pass on the favor that some very kind strangers on the mustang forums have passed on to me and lead me through the dark and costly vast world of SBF performance parts. There are a lot of good parts that dont work well together and cheap parts that work great. It really depends on your situation and preference.