Shouldn't be required.
Just checking - did you buy a new compressor or a re-build?
My rebuild had the wrong pulley & I didn't notice until after the thing was all back together again! The rebuild has a strong possibility of having an Integra pulley, which is smaller - the compressor is the same so they use the Integra units as the cores because the're obviously more common.
Just something to look out for as it's not immediately obvious - may not apply in your case of course.
I would recommend going to an A/C shop for a pump out first before you start, then return when you're complete after the h/ware install to pump again before re-fill. They should give you a credit for the R12 they remove against the new material you put back (might even be your own freon if you're sticking with R12!)