Granted, I'm not hauling 8 people around, but I've never had any hill climbing experiences like you describe with my 3B powered Troopy. I have driven it up to the Eisenhower tunnel (elevation 11,150ft), Vail Pass (10,600ft), Wolf Creek Pass (10,800ft), and others. Never went into first gear. Not sure I ever went into 2nd on any of those. Don't think so, but if I did, it was only briefly 'cause some d*cktard cut me off and I lost momentum. There's a section of Boulder Canyon called "the narrows" that's over 10% grade (which is damn steep for most highways), and for a short distance on that I might have to go into 2nd, but as soon as the steep bit is over, it's back to 3rd, then 4th by the time I get closer to Nederland.
Maybe it's just the extra weight you're carrying, but you might want to check a few things that might be slowing you down. Are your brakes dragging? When did you last adjust your valves? Compression still good? Fuel mixture and timing OK? Injectors? Not much to go wrong with these motors, but they should do better than what you've described. Are you getting a lot of smoke? Is it getting unusually hot?
Try a run up a hill without passengers--just empty--and see how it does. If it's still as slow as you say, you need to figure out why. Something's up.