will a set of heads really change performance

[71Seth]

I have a sb400 in my 71 c-10 which has been pepped up a bit with .040 over with speed pro flat tops, comp 292H mag. edelbrock rpm performer intake, 750 holley duel feed, accle super coil we put a set of valve springs on but dont remember what they were. But it still has stock heads. I feel like this engine has great potentale right now but the poor flowing heads are killing it. What is a good set of heads that will flow good and give a performance increase w/o completly digging out my pockets. I like the look of aluminm a lot. better to buy complete or bear heads? Should i just look for some double humps? what sizxe cc should i get.
thanks seth