Welcome to the forum. I'll give you my thoughts, and others can chime in with theirs. The 348/409 is one of the coolest looking engines from that time, with the unique rocker covers, and thundering exhaust note. In '58 Chevy was scrambling to respond to Ford's continuing growth of their Y-blocks, which went from 292 to 312 to 332, and it had been leaked that it would be 352 in the new model year. Short on time Chevy grabbed the 348 from their truck line, cast a 4-barrel intake for it and dropped them into the full size car line. They have some unique design features, one being the wedge shaped combustion chamber, and you won't find nearly as many after market parts for them as for the small blocks, and it's not easy to build an efficient, good mileage engine with a 348/409. They were raw power plants.

Right now you have something that would be of value to someone looking for a time period numbers matching restoration. Once you take it apart, you're going to find that it's a money pit. Since you've been honest and told us that you're a woodworker who has an interest in the engine, the best advice I can give is for you to advertise it in Hemmings, and sell it as-is. If you can get it running without tearing it down, just to prove it runs, you might consider that but given your experience level, I'd leave it alone.

One of the guys here, 53 Chevy5, had a beautiful 348 in his pickup, and after a few months chasing overheating issues and stopping at every gas station on the highway, pulled it and replaced it with a LS engine & tranny. He just recently sold the 348, and maybe he will offer you his advice. Best of luck.