check the ports to see if they have had work done to them. standard ports and NA is balls!
measure the cams as you'll want larger lift than turbo cams. measwuring them will help determine if they are standard or not.
check valve size and head depth. too much skimming means they are no good for turbo and better for NA. but to thin does not mean set up for NA. what vale springs and followers are in it. Solid lifters are better for NA.
Of course there is alternate argument to all above in the magic art of engine buidling.
JP