I have not been able to figure out which engine this is, the number stamped on the front left of the block is N4506 with the casting number in the rear 3892657, I don't know how to figure out from here which motor this actually is, 302, 327, or 350?

This motor is in my 1970 Suburban which came factory with the 400, from the research I have done, my motor is highly desirable and would be more than willing to trade for a 400 like was original. PLEASE HELP.......... I have been looking everywhere and nobody has been able to give me an answer, thanks!