Crank pulleys will not bolt to balancer

Good you are sticking w/ the cast-iron water pump. I used the later alum w.p. on my 273 (to match new radiator) and it caused a cascade of issues. I had to change to a later Federal p.s. pump w/ brackets, re-position my alternator and get creative w/ the belt routes, plus the extra 1" thickness made it hard to get a fan to clear the radiator. Crank damper thicknesses varied over the years (I think) and many combinations of pulleys, so can get very confusing.