The pontiac grand prixs of my style are the 97-03. They are sideways mounted engines. I run Royal Purple full synthetic oil with ROyal purple glass wool oil filter. I will also use lucas synthetic oil stabilizer as well. I now have 107K miles on my grand prix.
I think the 20-50w in the Transport will cushion the worn bearings fairly well. I hope to get quite a few more miles from van...cheers