Well, since putting the V8 back together in something of a hurry, I've covered about 6thousand miles, relatively trouble free engine wise. So, I'm fairly confident that the conversion is straightforward.
The engine I used was likely much higher mileage than indicated in the paperwork, but is pretty strong.

It does however have 2 outstanding issues-

A persistent oil weep at the back of the left cylinder head which I initially presumed to be either distributor or cam cover gasket related. Not a major leak, and it really only happens once it's warm.
Some further investigation is required.

It blows a little oil smoke when pulling away. Not a huge cloud of smoke, but it's there. So, given the mileage, I'm planning on stripping the top end in the near future with a view to putting in new valve guides and seals.
I need to find a good valve spring compressor- the one I have doesn't have sufficient reach to clear around the head. So if anyone can recommend a particular make/model of handheld spring compressor, it would be useful.

Cheers

85 WR quattro
90 V8 Silver, 91 V8 Black, 93 V8 Lago
93 100e quattro V6. Titan, i think