That Manitou II is probably as close to ideal for what you want as you are going to get in a kayak. It is wide, but for a cargo hauler and at your height and weight you are probably not going to love anything narrower. You can haul bulky objects in that front cockpit. The thing to check with polyethylene used boats is that they have not been stored exposed to sun. The weight would concern me a little for loading on foam blocks, I would want roof racks myself.
I decided against getting the kayak. It would require a 4 hour one way trip into the valley and then hauling the boat back on my car on the highway and also the freeway. I’m waiting out for something local.
This kayak I think might have worked well, but I’m in no rush. Hopefully there will be more options come up on craigslist in the fall.