Wonder if the 16F88 would work as a replacement. I started with a 16f628 (doesn't look like it supports AD either) and ran out of space, so went to the 16f648 without having to change any code. If the 16F88 will work with only code changes and no circuit changes, then that may be the way to go. Sure wish there was a side by side comparison of compatabilities for the different chips somewhere. Some areas of the data sheets don't make enough sense to me yet to know what the differences are.