My idea is to find a good used Apollo GX-50/GX-60 unit and replace the
ADF. No need to touch the Loran, it makes a good backup.

I have a GX 60 NO 1, Gx65 NO 2, Radar Altimeter, Annunciator, Glideslope, but
the main and most used GPS was and is a 195, 295, 196, 296 in that order of
purchace. Outside of the comm the portables have a lot more features. Look at
these closely before you buy a GX 60 or 430.