Apparently so. Internally balanced 273-318-340 harmonic balancers are supposed to interchange with the Poly A engine, so that sounds like the Poly harmonic balancers are the same. See http://www.1962to1965mopar.ornocar.com/poly318_1.html Thanks, Gary H. Bill wrote: ... > Is there any reason that a harmonic balancer from a 66 318 Poly would > not interchange w/ a 65 318 poly? The donor motor I just got has a HB > w/ a timing mark on it where my 65 HB does not...just making sure it's > a straight swap. ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html.