Engine out

I don't know when, but I'm going to take the Pantera engine out, and I'm mentally preparing. The reason it's coming out is that there's a oil leak into the clutch area, and I think it's engine oil. The engine runs fine, compression is good, oil pressure good, it has 74k miles on it.

Some advice needed to save me some time and money...

1. Is it easiest to take engine and gearbox out together? What do they weigh? Anything special to be aware off?

2. What does an original Cleveland like this need? If it was a Chevy SB which I've restored many, maybe just a timing chain, oil pump and gaskets? I guess a Cleveland needs a harmonic balancer after reading these forums? What else? Please don't say total restoration if not needed I don't drive on tracks, only the occasional blast around town or through Europe on unlimited highways but rarely above 130 mph. Engine has new intake (Edelbrock Performer), carb (Holley 600 vac), water pump and fuel pump.

3. What about the gearbox. That works perfectly as well. Any gaskets/seals that can be changed? If so, where can they be bought?

4. Any further advice?