I remember seeing the van on retrorides for sale and drooling over it,what a minter.
I'd be cautious of the di,although bombproof their very gutless,with a car on the back they really struggle,perhaps a turbo one would be ok but for similar economy and much more fun go for the cossie granada lump,their gonna be pretty easy to fit and much more modern.
If staying diesel a nice e300td lump from a 90's merc would be the boy,I'd leave the autobox on too as their super tough as well.
These are the ones that can be tuned to ridiculous power on boggo internals,there's a drift merc estate doing the rounds on this very engine with a silly sized turbo on it!!!
Not saying you'll go huge power but at least you know these motors are super tough at about 180bhp and 300nm torques.
Really looking forward to seeing this finished.