Honestly, what would you do?

[Puyallup68C20]

I bought this 68 C-20 about 3 months ago. Prior to that it had been sitting in a field and ran a few times during that year to haul some manure around the farm. Prior to that is any guess. It has the original 327 and Th400, drums all around and power nothing. My buddies and I just did a "tune up" yesterday. All along I have known that it does burn "some" oil, and we fixed the problem of oil loss coming from the oil filler being able to just pull out with ease. The plugs when we pulled them were terrible looking all gunky and covered in oil, my buddies were amazed that the engine was running "fine" with them in that condition. We replaced the plugs, wires, cap, rotor, and properly time it. During this process we realized that the steel crank bolt had in the past been broken off halfway or so in the engine. This quite worried me considering I don't want to have my fan and stuff flying off. But his father said its been in there for 50 years so far and hasn't come out, but best to take care of it soon. So my plan is for a rebuild. My buddies say lets get some serious HP out of this engine, I'm thinking lets keep it original. But I know barely nothing about all this stuff so I rely on many gearhead friends to help me out along the way so I to some day can tear it down and build it. I know on this forum with all your knowledge and experience, that you guys would know whats best for this situation and how I should go about it. My buddy knows a guy that can rebuild it for say 600-700$ I could have a bit extra cash saved up by then and perhaps do some modding to the engine. What would you do?