Yeah you read it right Marki, the heads in that ad have the standard size valves and the exhaust valve of a buick 300 ally head is indeed smaller that that of a rover head. That probably means that the original seats are in place which may not be compatable with leaded fuel. To be honest no-one buys buick heads and leaves them stock, the whole point is that they are a better base from which to start a performance head build-up. Yes the chambers are bigger too which could be useful if you're building a turbo motor. Gregg55 is a good person to speak to re the buick heads, he knows a great deal about them and can advise. I have a pair of these heads myself, i've stripped em, taken seats out, blasted 'em and dipped 'em! and also had them annealed ready to weld up those big old chambers. However there is some damage to my heads, slight on one head and heavier on the other. Gregg passed a pic of the damage onto another buick expert for me who says its corrosion and not to worry but others who have seen it expressed concern that it may be porosity

Apparently this is common on these heads. Also there were two batches of castings (despite them only being available for one model year!). The earlier batch have the smooth rounded style quench pad behind the plug and the later batch have a triangular shape pad. There are also some other different casting marks but the dimensions of the heads are the same in every important respect, a good job really considering my "pair" consists of one of each type! It is said that the later batch are of a higher casting quality and this is evident in my heads. I will keep an eye on the auction though as this pair seem to be ok and may be worth a punt if the price stays low but i am slightly concerned that they have been rebuilt to stock spec! the only possible reason to do this would be to unload them more easily as "bolt ons".