Pulley alignment advice needed

[Belairbob]

I have the correct pullies for my 72 w/350 but the alternator/WP/Crank belt is off. I have a new water pump that measures 5 3/4" from the flange to the machine surface of the block. I have read that it should be 5 5/8". I could be closer to alignment with that 1/8" difference! Do you think it is possible to drive that W/P flange a little futher down on the shaft? That would be with
removing the back cover and positioning the end of the shaft on something solid like an anvil and maybe use a socket against the flange when I hit it with a hammer. Crazy?

Thanks,
Bob