Hello Mike,
I am glad to help. Please accept my apologies if my last response was not clear.
In case you are using exactly the same devices with different packages, please be aware about the pinout in order to use the same .hex file.
If the pinout configuration is exactly the same, I mean, if you are using the same pins contained in both devices, you can use the same .hex file.
If you are migrating from 40 pin DIP package to 44 pin PLCC package, I do not see any problem to do it :smileyhappy:

Hope this information will be useful for you.
Have a great day.
David