289 cylinder head on 5.0L????

the combustion chamber volume of those early heads is ALOT smaller than late model heads (like 54cc's compared to 62) so you'll have some crazy compression, and there's no thermactor inlet in the back of the heads as well as thermactor bumps in the exhaust, but you can easily bypass the smog pump. Another thing you'll have to do is get some sort of pushrod length tool (i believe many camshaft companies offer a pushrod length tool) and take it from there. You may or may not have to change pushrods because i don't know if the geometry or height changes when you use the rail type rocker arms of the early heads. You'll probably end up having to pay alot for gas and retard the timing becuase i think those heads will give you over 10.5:1 compression, probably near 11:1. I'm just talking out of my @ss on this, but i'm sure there's at least one person who's done this on this site. Good luck man!