I'd clean it up and assess. Hard to believe all of those things are leaking. Starter is the drain point for the hold down on the valley pan up top. Anything coming from on top of the engine is going to run down the rear passenger side of the engine/transmission. Spray down the valley pan with carb or brake cleaner and see where it comes out underneath.
Transmission lines have been spliced with soft hose. Replace that with new hose.
Oil cooler can be disassembled in frame or the motor mount can be removed and engine jacked up to pull it.
Someone cared about that truck enough to put in a newer gp controller and it looks like they put a block drain at the oil cooler, have had the valve covers off and rebuilt the transmission.
These engines shouldn't have an oil pan gasket installed on them although you can buy one. That's the only thing you'd need to pull the engine to reseal.
If you've got the time, pull the motor. But you won't know exactly what is leaking so you'll need to reseal everything whether or not it's leaking. Good time to massage the body seam for the turbo you're going to install
If it was mine and I pulled the engine, it would get studs, new head gaskets and valve seals at a minimum. You may want to check the rockers and update them if they're original when you pull the valve covers. It sure is easy to spend someone else's money.
What do you mean by the flywheel screeching? Are there some chewed up teeth on the ring gear?