as far as I'm concerned, a td head has one thing, td exhaust valves. nobody has really proven one way or another that the material is any different, or that it matters, I've run all configurations, even using na valves in td's with no adverse effect... anyway, I need any good mechanical heads, not just td..
my ideal going price for good head cores (meaning only cracks are in between valves, cam journals aren't all scratched, and are flat with a machine straightedge) I would guess is 75 - 150 depending on condition. 1.5 would be an option if I were desperate, but for now I'd prefer 12mm 1.6 heads.