This is the one used in Ireland after the war, and it was an Austin Series 3 body on a Peerless chassis.
Ken Musgrave did the plans for a Peerless lorry, so that would have the wheelbase and track, and plans for an Austin Series 3 or Austin 1918 would have the dimensions for the body.
I thought I'd read that it was just a straightforward Austin body on a Peerless chassis. I believe in one of David Fletcher's books. That's why the body is too small for the chassis. If they changed the bonnet, why wouldn't they have changed the rear as well, to use the extra space?
Anyway, if that's correct then, yes, you could use the Austin body on a new Peerless chassis - just like they did in real life.
Pattern 1919 is what it is called, AFAIK. there may be slight differences in body proportions, as to my mind the Peerless is more handsome than the Austin, despite the chassis rails sticking out at the back.