It will be a bit longer for the beaver-tail and I'm playing around with a possible fibreglass roof with actual corner curves but your picture has really helped with the visualisation.
Glad to be of service! I did try and find a picture of the Healy to put on the back, but I couldn't make that work very well. Agreed about the extra length, not only will it look better but I imagine it'll make getting the car on and off a lot easier.
Still a work in progress I'm afraid (it's getting late) but the basic idea shows through. The deck is recycled from a lightish transporter, Renault, Iveco, that sort of thing and the cab cap is from a more modern truck. They are usually fibre glass so you can chop it about to suit. I envision it with a bit of an overhang at the front so that it forms a sun visor. Put a hatch in the cab roof and there would be access for storing light stuff. The tyre rack could extend back over the bonnet of the Healey if height was an issue. Storage bins on either side of the chassis for tools etc and you are sorted!. Don't know if you'd want to travel very far in it thought as I remember the Bedford RL as being a bit slow, noisy and uncomfortable, mind you, I was usually bouncing around in the back (I was a squaddie) Lots of good stuff available for Chevy and GMC sixes, so a man of your considerable capabilities ought to be able to make the beast boogie a bit and probably run on LPG too. I shall watch with interest.