Hi, that's a nice specimen! Yes, the wheels and cord are later replacements - the original cord was always black with a generic Belden end, and the wheels were dark blue.
You mentioned it only has "so-so" suction. I wonder why that is. These models are quite powerful when running properly, especially with a completely sealed hose as you have there. When you shut it down there's some rumble in the motor so I wonder if the suction fans might be clogged up and thus full suction might be impeded. It should have really good suction.
Also, while it does not sound like there is one, you should open the rear cover and see if there is a filter pad in there. If so, remove it. You can save it if you want to, but don't leave in in there. It only restricts air flow and if you use the machine long enough, the motor will heat up.
Thanks for the pix and video! I thoroughly enjoyed all!