So I noticed that some other people were advised to change out his exhaust seats and valves to cope with unleaded gas. I'm pretty sure that I want to do the same for my 255 merc motor, but I'm wondering if at that point, should I just have the motor rebuilt??? Is it possible and/or even worth it to swap the valves and exhaust seats out without rebuilduing the motor??? I've never replaced either of those parts so I don't know how to do it or how difficult it is. Also, I was eventually planning on upgrading my intake manifold and heads. I wanted to slap on a set offenhauser heads, but I'm not sure if they will work if I'm running a stock bore and stroke. I know that edelbrock makes heads that will work with a stock set up, but I'm not sure if I want to go that route. As far as the intake manifold, I want to go with a Baron racing PM-7 Thikstun dual intake manifold with two stomberg 97s(http://www.baronracingequipment.com/...lManifold.htm). Does anyone know if that combination of the baron intake maifold and offy heads will work well with a stock long block? I guess that my goal for right now is just to pep up the asthetics in the motor compartment and I'm not building a race motor wich is why I'm slightly reluctant to start throwing together parts that I'm not sure will work well together. Any advice would be appreciated. Thanks!