That is just the EFI manuals
There is also the drive manual, base engine manual, controls manual and cooling system manual
However for torque numbers, just Google SBC fastener torque
Do a compression check.
If you pull the heads, look at the ridge. If you can catch a nail on it, then rebuild.
Pull the pan and plastigage the bearings.
At 80k, I would probably only borescope the cylinders when I went to look at it
If your motor was ever run in salt, the damage is done. Adding a heat exchanger may slow the corrosion, however the rust will plug the heat exchangers.
My suggestion. Run the boat until you need a new motor. Then add a HX at that time
