Call JimV and talk to him. He will have great info for you and maybe a set of used heads from someone who upgrades.

I'm with jjones boating season is way too short to worry about $ spent on the boat

ITS BETTER TO ASK FOR FORGIVENESS THAN ASKING FOR PERMISSION

Go for it and let us know the power results

Jeff, I'd snatch up those "049" castings from your machinist!!! I didn't originally see this when you posted it, but the 353049 castings from GM (we call them "049" castings) are an excellent head for your engine. They have the larger oval ports than the "peanut ports" you have now, but you'd still need to do the bowl/pocket porting work with them. You can even install larger valves as we used to do back in the 1980's. However, as with any stainless steel valve you will still need to at least install hardend valve seats---at least on the exhaust side otherwise they will sink---we went through all of that back in the day.

Anyway, you'll be much farther ahead with the larger 049 oval port heads vs the peanut ports. Also, if I remember correctly "JimV' told me that the 049's don't flow much past .550" lift---even after porting so, you obviously don't want to cam it much beyond that.

Will Gen IV head castings work on a Gen V engine block???
I do know Gen VI heads work on Gen IV blocks. Gen V blocks have real big core holes at the head surface. I'm thinking that combo will leak...

Pat, I really don't know! I know you brought that up before and I completely forgot---good point!!! My bad. Are you sure there isn't a gasket that will allow them to mate without leaks? I'm going to ask around.

I have heard of special gaskets for the Gen V blocks but I have no experience using them.
When GM retooled for the Gen VI block and head castings they fixed a lot of the incompatibility issues that exist with the Gen V castings. The after-market companies have designed their heads to work on all generations of blocks.
It sounds like we have a good topic to start another thread...

Just wanted to keep you guys updated. My machine shop had a set of 820's from a 71 454. I am having new hardened seats installed on the exhaust, severe duty valves, 2.19 & 1.88 and I am using the guild plates, rockers and studs from my other heads. I am going to do some port & bowl work and I should be ready to go. As far as the Mark IV Gen V compatibility goes, I have been told a Mark IV head will fit a Gen V block with Gen V gaskets. A Gen V head will not fit on a Mark IV. Should have about $850 in the heads with me doing the port work. I will let you guys know how it turns out.
Thanks,
Jeff

email me [email protected] and i will send it to you.

call me im in st charles mo 314 265 3876