Welcome to the site.
IF you're dealing with the original '62 engine it will be easier to do than on the earlier ('54, '55, '56 (?)...) valley pans. My recollection is that the early y- engines did not have notches cut in the edge of the valley pan sheet metal perimeter to help in clearing the intake ports on the cylinder heads.
I can't remember when they began adding those, but I believe the early valley pans did not have them. BUT, I may be mistaken, too!
Getting old has consequences!

ALL of the previous input on this was good. It seems like Dan covered ALL the nitty-gritty particulars well.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York