What year is the 525 boat? I believe 05 and a half and 06 was the change over year for headgaskets and head bolts. Look at the head bolts, if they have a con-cave and a plus sign stamped they are gm junk and you should pull the heads for refresh. If they are arp leave the heads on and do springs, retainers, locks. Contact Eddie Young about which springs and retainers to use, he has a recommended setup over the stock pac springs.
Also look at the header tubes by the cylinder head. If they remain the same circumference the entire way to the flange they are the older style cmi’s(ran 350 hours with no issues with ours). If the tube gets skinnier before the header flange those are the revised headers. When you do the valve springs just pressure test them with a garden hose for reassurance.