Neil:

I'd suggest that you not try to duplicate the rigid copper
propane lines but use more modern flexible ones.  Myself,
I'd run one from the tank regulator into the cabinet and
then split it to the fridge and stove as necessary.

Any RV repair shop should be able to help you with the
lines you need.

When I added my second tank (7 years ago) I bought a flare
tool and tube bender.  Whew!  More practice needed when
I only needed a couple of flares.  That's why I'd go with
flexible now, for sure.

Richard