For Jacobs, I'd pictured James Spader. He's a favourite actor of mine and I think he could play virtually anything. To paraphrase a quote from Kevin Smith when talking about Ben Affleck, I think that Spader could play the shark in a remake of Jaws heh.
For Morton, I saw Edward Furlong. His life somewhat mirrors Morton's, and I always recall Furlong's grungy look from T2 when imagining aspiring young rock stars.