No, I dont know anyting about "buynsell", if i want used auto parts i will look on either craigslist, ebay, or racingjunk.com. I rarely go after used parts though (besides a block). My favorite company to deal with when buying engine parts is competitionproducts.com. if they dont have it i will look into summit
I believe in the concept of "you get what you pay for" and nothing rings truer than with motors and cars. the only iron heads would consider buying are the DART Platinum heads, no other manufacuter compairs when it comes to iron heads. For these platinum heads you are likely going to spend around 750-850 for a bare set, then have them cleaned up a bit and assembled you are looking at another 550-750. then when it comes to alm I like AFR, DART, and Brodix. Pro-filer, the old EQ and RHS make decent heads as well. to have a set of alm heads in the condidtion that i would run them would cost me around 1900-2200, which is about what i have into the heads on my motor right now, but they also flow around 315-320cfm @ .600" and on the dyno they made a great tq curve.