Re: 5.0 5.7 Vortec heads
Wrong!!!
Do your homework and read the other posts. This has been asked and answered. As stated above the part numbers for the heads are the same...
10239906 12558060 12558062 are the "real" vortec heads that everyone wants. The '906 casting has a hardened exhaust seat that reduces flow so you might want to stay away from that one if you want pure performance but the hardened seat is preferred for regular marine applications.
The 5.0L also came with vortec heads 12558059 but they are different totally than the "real" ones for a 5.7L. Similar but different. Combustion chamber is smaller and not heart shaped for starters, runners are slightly different as well.
These are the heads you get from GM when you buy a 5.0L in a truck.
And they are the correct size for a 5.0L, 58cc
I am surprised that Mercruiser uses the 350 heads on the 305 as they are not the same.
Gm marine engines use the 059 casting afaik.
I sure hope so as I have a set ready to bolt onto my 898 along with a performance products manifold and edelbrock 4bbl.
But I agree with the other people and recommend that you rebuild the 5.7L with the marine stuff from the 5.0L.
Good for about 60 more hp.
You will need to reprop and/or change gears in your upper unit though.