how much to ask for X heads?

$300. is not bad for assembled X heads.

I paid $200.00 for mine about 6 years ago. They had good valves and springs already installed. I put another $227.00 into them to have the hardened valve seats and new valve guides installed as well as a valve job done, decked 10 thousandths and reassembly. I have $427.00 in them already and I am thinking about having them ported so the total is bound to rise!

Good Luck with the SALE!