Hi Kirk, If you loosen the fan belt and maybe even remove from the pulley on crankshaft. Then get you a really bright Led flashlite and a mirror so you can get the mirror down next to the front of pulley at about a 45 angle, then shine your flashlite into the mirror, you will see a line around the front of pulley about 3/4 -1,1/4inch in from the outer edge of pulley. that line is where the outer ring of pulley is bonded to the hub/center of pulley/hub. that bonding material is about 1/8 inch wide. Yes the dealer will tell you that you have a one piece pulley because those 2 parts are not made to be serviced seperately. If and when you have to service that hub/pulley assy ,because, (ex:chunk broke out of V groove, bolt came loose in centerof pulley/hub allowed center hub to wobble on crank, bonding material protuding out, etc), you will recieve a complete pulley/center hub assembly ready to slip onto crankshaft. You will also note a notch in outer edge of pulley, that notch is for those timing marks I related to in earlier post. You may have to remove/pull that pulley assy off the crankshaft and mount it in a vise with protective material covering pulley where seal runs, then take a strap wrench around outside of pulley to see it turn/rotate seperately from center hub. Put a white paint mark across front of assy to see if it does turn seperately. One other thing that may possibly cause an overheat problem is if there isn't a thermostat in the coolant system. On the old smallblock Chevys, 283,327, if you took the thermostat out , the coolant would get to circulating to fast thru the radiator for it to cool down the coolant.. Also if you look in the thermostat housing on your 28N, you will see that the thermostat does 2 things, it opens to allow coolant to radiator , but it also closes off the bypass port that sends coolant back into block coolant passages. If it has wrong thermostat in it that doesn't do both of these functions. The coolant will go to the path of least resistance, and that may be just around and around the block. I know this is long , but if your like me , I'm open to any help when it comes to difficult problems to solve. Hope you solve yours.