There's not much need for me to point out that my replies to these questions will be coloured by the fact that I am an absolutely massive fan of this conversion, I had mine done in early 2008 and it's been completely reliable apart from point 1.
Are there any reliability issues in the longer term? I notice on Morganatica a report of an electrical connector failing and causing a fuse to blow but this seems to be easily remedied.
This happened to me on a motorway in Belgium in 2008, shortly after I had the conversion done. The electrical bullet connector on the bulkhead that feeds the radiator fan came apart, and this blew a fuse. The resulting error code put the engine into limp mode, so it would only run at just over 2,000rpm. Reconnected the fan, replaced the fuse and it's been perfect ever since.
I have done some routine work on mine (Cambelt and Camwheels, Alternator Belt, Oil filters etc) and have no probs getting stuff from my local Vauxhall dealer - in fact they were so taken with the conversion they made me an honorary member of the Astra Sri club so the could give me a discount.
How does the (I think) Salisbury rear axle cope with the extra power over the long term?
I had my rear axle rebuilt by Billy Bellinger in 2012, the diff was a bit worn (not because of the new engine) but mainly I fancied a Quaife LSD. I also fitted anti-tramps and a Panhard rod but they aren't strictly necessary.
Any feedback on whether the cars are worth more or less than standard on the market?
By rights they should be worth more because you get a 165bhp 4/4 with absolutely stonking performance, but of course people are obsessed with originality so probably not.
Any issues with the chassis after being opened up for the exhaust exit?
None whatsoever.
Any significant difference in weight compared to the CVH engine?
It's a bit lighter, and ground clearance is a bit better.
I'm not sure which gearbox this car has? I believe some have the original Ford, while others may have alternatives transplanted?
Kevin did the prototype with an Omega 5 speed box. I think all the other were done with the original Type 9 box, mine and one other definitely have, but I can't be certain about the one you're considering.
Anything else which might sway a potential purchaser?
If you really want a 4-seater, then it's probably best to hang on for one. If you want a 2-seater that goes like absolute stink, wails like a banshee all the way up to 7,000 rpm and is a complete hoot to drive, then this car will deliver in spades. You need have no fears about reliability or the quality of the conversion. I have obtained all the technical information on the setup from Kevin Vernon and have the software necessary to edit the ECU configuration so there's no need to be concerned about the knowledge being lost - but having said that I haven't touched my setup since I had it done, I am perfectly happy with it.