1. I replaced the tracks in my 48 with plastic. Don't remember where I got them - think it was an RV supplier. Keeping the drains open will prevent water leaking inside.
2. Too many pieces to rattle loose. UGLY!!!! KC's welded rails can't be beat. STRONGLY suggest you replace the missing/damaged with same as original. You probably want to tallerize your upper deck railings. If you have everything cut and fit, ahead of time, a good welder should be able to do whatever in 3 to 6 hours.
3. If tank is not taking on water you don't have any leaks. (GOOD) There aren't any inspection hatches (NOT SO GOOD). Follow Peggy Hall's cleaning instructions 2 or 3 times and Install a Pur or Britta filter on the faucet you drink out of. Your then good to go. NOTE: IT AIN' T BROKE DON'T FIX IT. This was one of KC's better ideas - lots of water storage in an unusable space and adds stability to the boat.
If you get over the fear in your mind you aren't going to get sick. If you do I was wrong. I always drank tank water, my wife drank bottled.
Fill your tank and use the ships system 100% and you will always have good water. I was always leery about hooking up dock water to the boat because of possible leaks developing and sinking the boat.
4. My friend added a foot to his platform on his 36' KC cruiser without adding additional braces. He fabricated pieces and added them to the original. (While on the hard) Looked factory when he was done. Get every thing ready and have the welder do the job when he repairs the rails.
Note: Some Kings Crafts were equipped with bronze cased cutlass bearings. This resulted in heavy loss of metal around lower portion of strut due to electrolysis. If yours are in bad condition have your welder build them back up and replace bearings with fiberglass cased units.