Tob, The casting# 366855 decodes as a GM (Chevy/Buick/Olds/Pontiac) 250 I6 used form 1966-84. To further ID your engine, please look for and provide the engine serial# which is stamped into a machined pad surface just to the left of the distributor where it's enters the block. You may need to clean off some paint and road grime to see the info. That can be used to further ID what you have.
