Don't worry about the distrubtion panel. What size alternator and what is the amp/hour rating of your house batteries, what kind ( flooded, gel ) and charger.
Then determine your loads to see if what your exsisting equipment will be adequate.
Ehh, I would worry a lil about a 30+ year old distribution panel that was built rather cheaply to begin with. Many original Catalina fuse panels that I have disassembled (I've owned 3 Catalinas) have had serious corrosion problems. Corrosion adds significant resistance, inducing lots of extra heat buildup that can melt cheap wiring & cause fires. Cheap electrical apparatus was not unique to Catalina. Electrical upgrades & repalcement of the original panels is a good investment, & the old panels will not be missed.
Plus getting rid of glassed fused circuits for modern breaker controlled switches is a must for reliability. Once you install a new 12 volt & 110 panel, then usually the original wiring gets yanked & replaced as well as the significant corrosion & rats nest of old wiring is usually apparent.
My original panels were also replaced with Blue Sea Brand, which are flexible in what circuits you want to add. But I agree that the overlap of the panels edge to where they screw mount to the board is exacting. There is only about 3/8" overlap. Measure more then twice, & hopefully only cut once.
ps. Installing extra 12 volt socket receptacles really comes in handy for powering portable 12 volt devices.
