how can you tell cubic inch of Buick Straight 8 engine ?

I have found an old Buick straight 8 engine and I don't know how to tell the year model or what cubic inch the engine is. How do I figure out if it is a 248 263 or 320 cubic inch? I don't know if the car it came out of was a Roadmaster, Century, Special or Super.

 

Check the overall length. If it is over 30 inches it will be probably be a 320. You really need to post the serial number to be certain. I see you only just posted the question. 9 pm Saturday here.

 

There's info online about head length.Smaller engines are about 30 inches,the 320 about 34 inches.As always,internet info is suspect,so double check with casting or stamped numbers or whatever ID the engine has.