5" Model 10s, while not rare exactly, are oft coveted, much like 3" by serious collectors, for a reason.
Modding Grandfathers heirloom... well, that's your call, but I'd leave it just as Grandpa shot it last and smile every time I take it to the range or do the fondle clean put back in safe thing.
Youth rebels, age conserves; between them, they advance. The Marines will cease to win battles the moment either camp achieves ascendancy. – Robert Leckie, Helmet for my Pillow