I think the diet will determine what he gains/doesn't gain regardless of what he takes. He's 140# @ 4% BF so it's not like he's shoveling food down his throat. So why would he gain much weight if he keeps eating like this? Keep the diet low key and I think you'll mostly get strength gain regardless of what you take. Don't oversimplify gaining lean mass ... you have to have a decent diet in place to make this happen.