motor knocking

[iride]

Hi all I have a 79 1/2 ton 4x4 that the only thing its ever been used for was plowing and the body is shot! It has a 350 and has always had a knock and i have babied it cause its mainly for plowing my long driveway. Yesterday i pulled it out of the shed and it locked it up and wouldnt start till i got a booster charger on it. It was stuck and when it came free WOW did it knock then!! I guessing its a rod problem it still has 20 lbs oil pressure and runs ok but is very noisy. My question is what can be done to limp it by till spring so i can junk it!! I poured in a quart of stp but didnt know if anyone had any other ideas. I dont want to tear the motor down its to dang cold for that! How many quarts of oil can I put in it and would that help at all?
Thanks
Todd