I've been looking for a Merryweather Jeep too, and it seems impossible, outside of the missions where they pop up. I didn't think to grab one at the observatory! Darn. I tried to save one off the cargo plane, as Trevor, driving it out the back, and riding it down to the last minute, but I could find it after it hit the ground (It probably exploded anyway). I guess I'm just going to have to start the entire story over again, when I complete it the first time. There are some other things I would do differently, given the chance. Without knowing the story out come, you don't know how to play it the first time through. And it's a long game too. Not that I'm complaining about that!