Replacing a 273 motor for a 5.9 360 Motor Question

Since the engine was rebuilt, maybe you can ask him if it was internally balanced, or what flex plate and convertor he used with it... If it's internal, any nuetral 10.5" flywheel can be used. If it's external, and needed either the B&M flexplate, or a weighted convertor, you need the 360 flywheel, or the template to have a nuetral one drilled to work with the 360. Also, if this is a later 360 (as in a 5.9L LA) the crank may not be drilled or finish reamed for the pilot bushing. So there may also be some minor issues to address there as well.