I'm just wondering about the pro's and con's of fiber-glassing a wood boat. Off the top of my head, it would seam that you are adding a lot of weight to the boat while making the hull stronger but perhaps slower.
What kind of things should someone be concerned about with that type of hull?
Just an opinion here from a wooden boat owner, but fibreglassing the hull of an old wooden boat - particularly one 75yrs old - immediately limits it's lifespan. If all you want to do is have fun for a year or 10, that's OK, but the boat is basically doomed in the long term.
Several reasons: Fibreglass doesn't expand and contract like wood fibres do and when the boat "takes up" water from the bilge and elsewhere, heats up in summer and cools down in winter they eventually break away from the inflexible sheath. Any damage to the hull - knocks, bangs, minor collisions, or just hard sailing in rough seas - also allows water through the fibreglass sheath and causes part of it to delaminate. This is fixable, but is a lengthy and very expensive job to do properly. Once a hull is glassed-all-over, it cannot be restored "to original" without replanking the entire hull - again, an expensive task.
People fibreglass-sheath wooden hulls for various reasons, usually because some of the seam were opening and they couldn't be bothered splining or otherwise fixing it properly. If you're serious about this one, you might like to ask them why it was done in the first place. Just because the boat is old isn't a reason to fibreglass the hull.
In any case, if you aren't from a museum planning to put the boat on permanent display on land and if it were me in your shoes, I'd walk away...