SFI 460 heads

I have been surching the web for months and found an absolute void on information about SFI 460 heads. I have ported a couple dozen DOVE heads and wonder if my (new for me) 89 SFI heads are just as corked up. I undestand that early heads won't fit. Can they be modified to fit? It runs like a dog and eats fuel like a hog. My old 400/2bbl will eat its lunch. So 1. do I have to port these things? 2. Will headers help? IT came with 3" flomaster, single exh. with a rammed out catylitic converter. All the rest of the smog junk is in tact. Bottom line is, can I liven up this dog and get a little more milage out of it too (I'm getting 10, loaded or unloaded)? I removed two plastic venturies in front of the throttle plate, and put them back in. They didn't seem to help or hinder. I also installled a K@N air filter. Still, not much response or change in milage. I can buy Motorsports heads, I know, but I have more time than money.