I did the same thing at my last house. Doors all had mortise locks with different knobs. Some were fake glass and some metal. Packed out the space from the mortise locks with shaved down wood. Glued and nailed them in before cutting new holes for modern hardware. No one in my neighborhood thought you could do it and most replaced the solid doors with hollow replacements.

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"I think I've cracked the code. double letters are cheaters except for perfect squares (a, d, i, p and y). So Leddy isn't a cheater... "