I'm in the process of rebuilding a 1965 18' HolmesCraft. It started out to be a refurbish only to find out it was pretty much rotted out. I gutted it and right now it sits with about 90% new framing. It is tarped for the winter. More work in spring. No doubt they are clutch head and come in different sizes. A good source for these is McMaster.
Here is the link.I am putting in all new stainless screws in the exterior and have found some nice Kreg Screws (a bigger head for exterior) from Amazon or from Hardware Sales.

Good luck. I think you will find the wood framing may not be the same size as today's lumber. It will be challenging.