I replaced my OEM converter with a Progressive Dynamics 9270 converter. Although my RV is substantially newer than yours, it is still not a modern RV. The only change that I made when I replaced the converter was to replace the converter to battery wire with a much heavier wire, #4 replacing the old #8 wire. The new converter now starts charging in the 40 amp range instead of the 5 or so amps the old converter charged at. The main reason for changing the wire was to reduce the voltage drop.
There is no reason to replace the DC distribution/fuse board if it is still working well. The question is can the old circuitry handle the higher charging current. It probably can since the discharge current has always been higher than the charging current.
Good luck with your project.