Keller in Bradford, if he is still around.. (between Covington and Greenville right on 721 last time I was there)
Name: Keller Gunsmithing
Street: 147 North Miami Avenue
Bradford, oh 45308-1013
Phone: (937) 448-2424
There is Mauser Man or something like that towards Columbus.
You would be best to have a smith do it, as there is a common spacing for the sight bases.. if you drill for a 1 piece, you only need to add the 2nd hole at rear if you were to buy and install a 2 piece.. I have that abiity with 1 of my Mauser, it is drilled correct for 1 piece, but I could install 2 piece if I want,,, the other ws drill random for 2 piece, but it will not accept the 1 piece base crorrectlly.
What pieces/parts you want for your 1911 fitted, most items is simple to do, but I would farm the barrel-link fitting/timing out to a person who does 1911 work.