Hey there Lemon Drop, sounds like a fun project. I took on restoring a 1976 Catalina 22 last winter and loved every minute of it. I stripped her down to just the shell and went from there. I decided to repaint the inside including the bulkheads and compression post and it really brightened up the interior. I did most of my accessory shopping on Amazon so will post some links to the items I used. I'll try to dig up some additional pictures if your interested. They are all just memories now as I just sold her a month ago.
After rewiring what wasn't embedded into the hull I installed a modern 6 gang switch/breaker panel in the original mounting location. The opening only had to be enlarged slightly. Just to the left I added two power meters that were tied to the battery, monitoring output to equipment onboard and charging input from the solar panel and outboard. I installed an additional thru hull connector next to the mast and installed a 50w solar panel on the front hatch using Velcro extreme. It was removed and stored under the v-berth cushions when underway This did a great job at keeping the Group 31 battery topped up supporting the boats meager power needs. On weekend trips we never even got close to running the battery down.
https://www.amazon.com/gp/product/B00W6JBUZW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B017TPHTLG/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B018ICLC3K/ref=oh_aui_detailpage_o06_s02?ie=UTF8&psc=1
These little guys came in handy when running new wiring inside the cabin.
https://www.amazon.com/gp/product/B003L16ZYU/ref=oh_aui_detailpage_o02_s01?ie=UTF8&psc=1
Light upgrade was one of my favorites. The indent running around the perimeter of the Catalina cabin where the hull and deck are joined is perfect for recessing inexpensive LED strip lighting. I also replaced the original stock cabin lights with upgraded models. It took two of the 16ft strips to run the entire perimeter of the cabin, including the v-berth. Each side is controlled by a separate dimmer.
https://www.amazon.com/gp/product/B00713R2ZK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0105KS4CU/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
Even though I also restored the sliding galley, I never used it a single time and it took up valuable space. As someone already posted, the butane stoves are awesome. We used ours on the cabin table.
https://www.amazon.com/gp/product/B002QUT3AU/ref=oh_aui_detailpage_o01_s02?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B001D7FYCI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Also do yourself a favor and vent your fuel tank through the stern and route your fuel line through there as well. To vent the tank I drilled a hole in the tank cap and screwed a brass nipple into it with a little RTV on the threads and plumbed it over to the thru hull vent.
https://www.amazon.com/gp/product/B004XAFICS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0009TNKCM/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
I employed a fairly simple but effective cooling solution on our boat last season.
Small, portable, rechargeable battery operated fans I found on Amazon. Initially I bought 1 but they worked so well I bought 3 more.
https://www.amazon.com/gp/product/B00Y1VZ3RO/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
These move a surprising amount of air for their size. They have an internal battery that will last for a couple of hours on high and a good deal longer on low. I have mounted 3M command strips on the bottom and back of the fans and can effectively snap them in to various locations on the boat. I place two on the bulkhead facing into the v-berth blowing directly across us while we are sleeping and I often have to turn them off/down in the middle of night because we get chilly. The real kicker is that these charge/operate via standard (unless you use apple products) micro-usb phone charging cables. Add a couple of inexpensive phone battery bank chargers and some 10 ft cables and these will run on high, all night for 2-3 nights.
https://www.amazon.com/gp/product/B017JL7DI4/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B016W06B04/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1
Another cool little trick I discovered when sleeping in the v-berth is that you can attach (Velcro) your phone or tablet to the sloped cabin top right above your head(feet towards bow) and use it as for entertainment, weather, anchor monitoring, etc.
Sorry, I know it's a lot but figured I would share some of my cabin upgrades.

I'm sure there is more I'm not thinking of.