I overheated the 425 in my Ninety Eight last night and now it is seized tight. Looks like it's time to pull it out again and rebuild it.

 

Or, it may have been vapor locked, if you got a cracked head or leaking head gasket and got coolant vapor in even one cylinder that would be enough pressure to seize the engine. If, after it has cooled you still can't turn it then you are probably right and have some siezed bearings.
That happened to a '76 98 I owned a few years back. #2 rod bearing siezed up tight.

 

I wish it was hydro-locked. I let it sit overnight and it will not turn. I have alrady pulled the transmission. I'll get the engine out Friday.

 

Ugh! I know the feeling of the knot in your gut. I spun a bearing on mine almost 6 years to the day. Odd thing was, I wasn't torqing on it or at high RPM so it was fate.

Glad to still see sings of life here. Do you guys visit www.oldsmobileforums.com ?