Knocking and loss of power

Welcome back. Knocking and power loss are not good signs. Usually this shows that the engine is very worn and the oil pressure isn't high enough to keep the bearings lubricated because of the wear. The "proper" repair would be to rebuild the engine or replace it with one with less mileage. What you could do is try using a thicker engine oil in it. Or add some oil viscosity modifier like STP to see if the problem lessens. If it does then wear is the problem and a rebuild or replacement would be a better long term option, if the rest of the truck is in good shape.