Hi David,
I put the tape measure on the Cobra trolley and it measures 1.5 meters long by 1 meter wide by 0.5 meters high including the castors. It's made from 75mm x 50mm by 2mm wall RHS tube.
The only things I would change If I built it again would be to raise the side rails that link the front to the back. It's a bit of a squeese to get under them on the garrage creeper.
One thing you might want to also consider is the position of your sump. I built mine with the firebird/camaro rear sump in mind. If you are running the Holden sump it might hit on the front bar. My sump hangs about an inch below the chassis rails and I assume the Holden sump will too.
trolley pic
As for the body, mine sat on a standard wooden fork lift pallett. It supported the entire floor and slipped inside the sills. The back of the boddy flexed down a bit so I supported it with a block of wood. When I dropped it back on there was no movement that I could detect.
My inner front guards aren't even either but with a bit of trimming you will hardly notice. I think the problem is that they are attached to the body in the mould and without some kind of jig it'll be hard to get them spot on in relation to the chassis every time.
Glad to hear you are making broom broom noises already. Leeroy has the right idea with the seats, I keep stealing the old cushion that the cat sleeps on in the shed.
Cheers