Valuable......perhaps to someone restoring a 340 car. But for the rest of us a 360 just makes more sense. I picked one up years ago for $75.00. Considering that you are buying an unknown motor I would much rather spend $75 for a builder than $1600. Building a hot rod, chances are you are going to stoke it any way. Nothing wrong with the x heads.....other than they are old. If I were going with iron heads I would just as soon buy a set of heads from Brian for $1500 than take a set of x heads to a shop and gamble on the casting still being usable....and when all is said and done probably be close to what Brian is getting for a set of new heads. But hey, it is your $$.....and your car.....spend you $$$ how you see fit.....