Hi dan14
Try this. Open 123.Drw and create a backup in different location. close 123.drw and erase not displayed. Open backup 123.drw, rename it, then open backup assembly 123.asm and rename this and save, then open 123.prt and rename this and save and close, now back to new 456.asm and regen,save and close, now you have the 456.drw regen, save and close.
Erase not displayed and try to open 456.drw and check that all parts have be renamed.
I have a question, if these are the same why not use family tables in part, assembly and control what part get used this way and have a variation table and/or a sheet 2 in your drawing.
If your using intralink the procedure is alot easier to do.
Tofflemire