As far as the triggerguard over the triggerplate, just file the "inletted portion" of the guard off so it sits on top of the metal of the triggerplate. In other words, notch it.
Very early guns might not have the guards inletted at all.
For the most part, though, guns closer in relation to most of our periods of interest, the guards are inletted, at the front, anyway. Sometimes they are inletted at the rear, sometimes not. Depends on the guard, depends on the gunsmith.