A friend of mine as a set of heads off a zz4 350, are they the aluminium heads found on 87 corvette's.

They were apparently ported by a very well known engine builder, although flow numbers were not provided upon purchase.

Are these any good, he is considering removing them to install a set of iron eagle 180's.

what should i recommend him.

thanks

They seem to have the same specs, but I am not sure if they are the same. Here are some unported flow numbers of the L98's.

http://i263.photobucket.com/albums/ii152/tjs69_photos/Heads/af5b.jpg

they are the L98 Vette heads, upgraded with better valve springs.
the early ZZ engines used the old reliable Z/28 springs, which got upgraded to the LT4 springs in the mid 90's on either the ZZ3 or ZZ4 engines.