WHOAH! Gasoline mixed with your oil AT THE VERY LEAST can cause CATASTROPHIC rod and bearing failure. Gasoline doesn't have very good lubricating properties(sarcasm...gasoline has NO lubricating properties), so when the gas/oil mixture that used to be just oil travels though your bearing journals, the bearings and rods, and cams and bearings up top are gonna tear the hell out of each other.
I don't care what anybody tells you, it is NOT common for ANY vehicle(that's not a two-stroke) to have GASOLINE mixed in with its lubricating oil.
I hope to Heaven you took your truck in to the dealer by now. If you have 3 or 4 quarts of gasoline in your oil, you've got VERY LIMITED engine life left. If the dealer verifies that you had ANY significant amount of gas in your oil, then your motor NEEDS to either be replaced or torn down and the damaged inspected. I don't know your dealer, but if they're the type that tries to kick warranty repair work to the curb, either take it somewhere else, or DEMAND that your engine be replaced or at the very least torn down and inspected. BOTH the top AND bottom ends.