400 small block engine good or bad??

I've got a 400 sbc from a '72 caprice. I've got it in a '78 camaro, and i'm tryin to make it a real fast paced car. I like to get out on some back roads and really lay it down if you know what i mean. I have done some mods to it, it has a summit cam with .488 lift with a duration of 234 on both intake and exhaust, its got a edelbrock torker II intake and a edelbrock 1407 (750cfm carb). Its also got a high volume oil pump, and headers. what else can i do to get more out of my engine? i know a bore would help but what about heads, everyone keeps telling me that i can't put any other chevy heads except the 400sbc heads???  

To the best of my knowledge your correct. You can only use 400 heads on that block.  Check with summit or some of the other parts houses to see if there are aftermarket heads available.  Short of that, depending on your budget and setup, you can probably get your factory heads massaged a bit to allow better flow. You can cam up an engine till the cows come home but if it doesn't breath and the setup isn't right, your not going to get the desired results.  Check some of the back issues of the mag here.  Seems like I saw an article or two about package setups with heads, cam and carb that could give you some ideas.  
Hope this helps.  

i just got finished buildig a 406 on a 400 block that features edelbrock rpm heads for a 350.what you have to do is drill steam holes in the heads between the combution chambers using 400 head gaskets as a template.any decent automotive machine shop should be able to do this if you don't feel comfortable doing it yourself also you will have to use 400 head gaskets.the 406 i just built features edl-2098 top end kit rated at 410 hp on a 9.5 to 1 350 on the 406 with 10.5 to 1 with 750 hp holly carb i expect close to 440 hp good luck.  

i know that trick flow heads work with the water jacket mod that is in their instructions..