If it were me I'd give them a thorough and close inspection
before and after cleaning
. Look for damaged threads, pitting in the valve/seats, cracks, reddening of Bronze due to zinc leaching, dents from impacts etc. If the seacocks look great after a thorough going over and servicing I'd probably reuse them. I'd probably be less likely to reuse the through-hulls especially since you'll be changing the backing plates and the exact thickness of the hull/backing plate may change etc. You may also choose to cut the old through-hulls out to ease removal
of the seacocks.
You may want to improve the mounting setup over the stock arrangement. For instance I used fiberglass
backing plates that were epoxied to the hull
instead of plywood
stuck to the hull
. There are plenty of online resources that detail different installation
arrangements including adding bolts that go through the seacock flanges, what type of backing plates and sealants to use and that discuss the topic of bonding (connecting electrically) the seacocks.
Some of the more obvious things that I would also do would be to replace all connected hoses and inspect/replace all hose clamps/pipe, etc.
Good luck with the upgrade,