You will be better off to replace the 27C64 with a 28C64 or any 28C part up to (I think) 28C512. I believe they all have compatible pinouts, but you should check datasheets to be certain. The only reason to use the larger capacity parts is that they may be more readily available.

The reason to use the 28C (or even 29C) instead of 27C is that it is an EEPROM (or flash) and not an EPROM and so does not have a window which can lead to erasing.

IIRC, the pinouts for the non-volatile memory chips change between 512Kb and 1Mb, so from 64K to 512K they are pin compatible with each other, but not beyond 512K. Again, this should be confirmed by looking at datasheets.

To reuse the 27C64 you currently have, it would need to be properly erased, either with a UV light eraser or by putting it out in bright sunshine for a long-ish period of time.

I could copy the chip, but I'm overwhelmed with other projects at hte moment and certainly wouldn't be able to get to it for a couple of months.