GM 350 Oil Pan

The automotive pan will work just fine. I put an automotive Milodon pan on my rebuild.

There are a couple of caveats that may or may not be a factor for you though......

I have a book that says a standard SBC marine pan is 6 qt. capacity. I cannot verify this for sure, however my new automotive pan when laid side-by-side the marine pan was indeed about a half inch shorter which would indicate smaller capacity (the new MIlodon pan specified 5 qt. capacity). I never had to put 6 qts. in my engine prior to the rebuild to fill it up so I never quite understood that capacity reference. The book itself is very good and informative otherwise. The difference in the height of the two pans could very well be justified in the construction differences. I also ended up installing a new dipstick so I could not verify the difference in capacity from old to new after the install.
You still need to pay attention to this height detail. A height difference between the old and new pan (either higher or lower) could cause a problem with the depth of the oil pump pickup tube. A shorter pan might not allow you to install it without shortening the tube. A deeper pan might starve it for oil if the tube isn't lengthened. MEASURE ACCORDINGLY!!!!!!

Another thing is that a factory marine SBC oil pan has the drain in the middle (centerline) of the pan. A factory automotive pan has the drain on the side of the pan. My original pan did indeed have the drain in the middle of the pan so at least one of the authors facts were correct. This might be a concern when it comes time to do your first oil change and you can't get to the drain plug like you used to.

Hope this helps. Let us know how it goes.