If you search long enough, rebuilt heads could be had ready to bolt on for less than $800.
I also forgot to mention the venerable 670 closed chamber head. If your block has the chamfers on the cylinders for valve clearance...consider those.
If you need any help locating heads or have any questions, send me a PM.
Tom
Here is a nice set of #16 heads..date matched. For the Buy it Now price and free shipping..I see no reason that they can't be used as is. If you would feel more comfortable, have them pressure tested and checked for guide leakage/wear.
If they do need work, I see no reason why any work needed would cost more than $400
And as another side note...those #11 heads were rated at 265 HP on a 400 block. considering the 350 block is 17% smaller in CI, With the #11 heads, theoretically (and optimally with proper cam and carb) you are looking at 220 net HP on paper...and with overcamming, over carbing and poor flow..likely in the 160-170HP range.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.