Rivarossi _is_ a top-of-the-line manufacturer. The cars have excellent
body mouldings, and other manufactureres have caught up to their quality
only in the last decade or less. Their wheels are undersize and have
oversize flanges, though, so I replace wheels and sometimes trucks, too.
They use a horn-hook coupler in a non-NMRA draft gear on the trucks. If
you want to reaplce these, McHenry makes knuckle couplers that fit -
different ones for different car-truck combos. Body mounted couplers can
be used if your curves are at least 24" radius. KD makes long-shank
couplers for long cars. Weight is on the light side, even on the cars
with interior detail.
These cars are as easily modified as any other plastic cars. IOW - the
amount of work depends on your vision of the perfect kitbash. :-) You
can use brass side overlays for different window arrangements.