SPEED DENSITY QUESTION

Yes you can but it's difficult to get right. Here's the website for a guy that can do it. http://www.kennedysdynotune.com

His name is Bob Kennedy. Drop him a line or give him a call. So far he's the only person I've actually spoken with that says he can do it. He should also be able to tell you if it will be cost effective or not.
 
I didn't either but I broke down and bought the Jegs kit, one hour later the car ran better than it ever has, it idles fantastic, better fuel curve (not so fat at lower rpm) and I can run higher timing than with SD, not to mention I can run any set up I want when the new combo goes in. Spend the money or peice it together you will end up with a alot more options open to you and a car better able to deal with your modding.
 
It's been written many times, but I'll do it once more: you can run aftermarket heads and other mods. The only caveat is the cam choice. You must maintain engine vacuum so you need lobe separation of 114 or more. Some of the Crower cams are commonly used.
 
I had an X cam on a STOCK engine in my 88 stang. It idled high (had to adjust the idle screw to keep it started) and it also surged alot. But I drove the car that way for a whole year before I pulled the engine. The brake pedal was very hard and sometimes the car was hard to stop due to the lack of vaccum. You really dont need to upgrade to mass air for an H/C/I on a speed density car its just that the cam cant be too radiacal (which mine was) and you need an adjustable fuel pressure reg to tune it correctly