I need to build the 340 block anyway so this might be a good option. I can buy whatever heads I need for it. I also found econo W2 heads for $350 each(bare)
You can either machine the stands down and use blocks, or you can use them as the econo versions they are. You still need offset intake rockers. Also, I don't remember the installed height for the econo' so but it is shorter than if you use blocks. If you go with the econo heads, make sure you check out b3racingengines.com and read up on geometry. You can use his shims to correct it.