I have a 1998 dodge ram 1500 v8 and theres a knocking on the right side of the engine and it sounds like its going to throw a rod bearing but not sure and it also has no oil pressure

deep lower engine knock can possible be whats called rod knock --where damage to a piston rod either spun bearing ,wrist pin,crack bent causing it to slap on crank or piston cylinder

Yes it will fit but why, it is a very poor engine choice as they are fraught with mechanical problems. the 5.2L is a better choice.

ok there is more going on here lifters out of adjustment more so if reving engine you bent a push rod or valve stem .

SOUND LIKE ONE OF YOUR ROD BEARINGS THROWED.

replace the ball joints and tie rod ends, and check the drag link!!!

5.9s are notorius for upper cylinder carbon build up and as a service manager I have used B G 44K thru the fuel as a first attempt with good results. The cheaper snake oil is a total waste of time. If that does not due it try the bottle fed option. FIND a B.G. dealer on the net.If you can, borow a boroscope,dude, you are not alone so don't feel frustated OR tear down an excellent durable motor.

If it's doesn't sound like it's your engine which i am thinking not. Check to see if there any heat shield that may have come lose, like the heat shield to the spark plug wire or heat sheild along the down pipe. 
Good luck and hope this was the rattling your taking about as it heats up it expands and tighten's up.

rod bearing , engine needs rebuilt

first of all standard or auto i am guessing its standed standard under drivers side hood near master cylinder there is a small clutch reservoir if there isnt enough fluid it wont extend the throw out bearing far enough for a shift because the clutch pedal is hitting the floor not enough fluid to extend the slave cylinder to drive the fork second faulty slave cylinder or throw out bearing as far as the light blown dash bulb or somone snipped the wire or took the bulb out

just the engine or the transmison as well