I use both Pennzoil Conventional and Quaker State Conventional in a blend with Quaker State Ultimate Durability in my M35. I use Smitty's Super S and Valvoline conventional in my friends' beaters.
Forumula Shell at Home Depot, tell them Mr. Handsome sent you and often times they will give it to you for free. Just kidding about the last part but the first part is true.
+1 and hard to wrong with Super Tech oils. Local garage near me uses GULF and they charge $1.90/quart. Other garage near me has stock of Kendall semi syn for real good prices