Great to see a Dodge forum! Dodge KICKS TAIL!

My 26' champion motor home has a 318 engine all original with about 50,000 miles. I just put a new pan,rear main and oil pump in it. I have done allot of updating with heavier leaf springs and front end to compensate for the added weight way above factory. It weighs almost 12,000 lbs fully loaded.

I had a 440 in storage i was going to instal in it..lets just say I don't have it anymore. Anyway I just got back from Texas now in Michigan, and other than installing a custom heavy duty drive shaft I have had few issues,,It's amazing the power this engine has and keeps going.

My question is what is the best non synthetic weight and brand oil I should use to keep this engine going till i can find bigger one. I'm going to spend some time in Texas than in Asheville North Carolina. Thanks much!