The migration document is long gone from MicroChip's website, the 16F84 replaced the 16C84 last century, and the 16F84 was in turn replaced by the 16F628, also last century - that migration document is long gone as well.
There's very little change required though, check the fuse settings, make sure GPR's start at the address (and if not, change it), for the 16F628, you also need to disable the analogue comparators, this takes two lines, and can be seen in my tutorials.