Re: new boat owner
Welcome aboard Holmstrom.
Looks like an Aruba! You can find some details about the manufacturer and the boats
HERE. There are also a few of us Silverline geeks and freaks over
HERE.
Diamondplate wouldn't be normal on the back of that boat, so either an enhancement or a repair. More likely it's the latter, but if done well it might be okay. Your test is suggesting the boat is sound, so it's okay to try it out on the water. Just be wise. If you've not already done so, a reasonable fee to a local marine mechanic may expose some unknowns or confirm seaworthiness.
The Chrysler OB's come with all sorts of opinions attached to 'em. Pony gave you some good ideas - definitely post over on the Chrysler OB forum. There's a guy on the boards who runs old Chryslers and has made 'em go for a long time. You'll get good advice.
Get a little training/instruction too if possible. A few hours spent learning from a friend, local Power Squadron or maybe DNR would be a few hours VERY well spent. Be safe!