All of the Tylenol deaths occured on 9/29/82. Two of the bottles were known to have been purchased that day. At the time, Tylenol was the most popular pain reliever and would probably move rapidly from retailers shelves. I think it is probable that most bottles of pain reliever would be opened and used within 24 hours of purchase. Therefore, it would be highly unlikely that all of the poisoned tylenol could have been placed on the shelves prior to 9/4/82; the day the Lewis left Chicago for NYC. The FBI concluded they were placed 9/28/82.
One of the bottles was placed in a store a mile from the Lewis's old neighborhood of Lincoln Park. The others were placed in various stores over a wide swath of suburbs west of the city. While I'm sure someone could get from the city out to Wingfield, 25 miles to the west, then 20 miles up to Arlington heights by public transportation, it is improbable. Who ever did it must have had a vehicle. (It is very difficult to rent a car with fake id's)
While Lewis's alibi isn't rock solid, its a real stretch to believe he could have made it to Chicago and back during that timeframe without leaving any trace. Since they were obviously short of funds, it seems strange that he would would spend this much money on a caper that would only cause trouble for an enemy and not earn him any finacial gain. (The "extortion" letter clearly was intended to "frame" Frederick Miller McCahey as there would be no way for Lewis to actually collect any money from the account he instructed Johnson & Johnson to use)
James Lewis is a sociopath with an interesting (and not particularly sucessful) criminal history but I don't think he did the Tylenol Murders.