I have a V8 90 and it took ages to find the right one 5 years ago, there were so many badly executed conversions with worn engines and ailing gearboxes out there. I didn't want a do-me-upper, or a project vehicle - I just wanted a truck to drive at the weekends and off-road (instead of the company hack) and have the best reliability possible with routine servicing only.
If it's an original factory V8 then it will attract a premium - there are not that many left in good condition and they have the hard-as-nails(if agricultural) LT85 gearbox, and four pin front differential. If it's in good nick and refurbed/well llooked after I'd agree with William, =A34500 seems OK - there's plenty of =A31500 rusty nails around with rotten bulkheads, worn transmissions, tired engines and thumping diffs that will soak up 3k in the blink of an eye and spend more time off the road than on.
As for reliability, the carb 3.5 V8 is probably more reliable than a Tdi because it's an old, low-stressed design with a cam chain and will take heaps of abuse before expiring. Received wisdom says they're aquaphobic (see link for a picture which would suggest not) - which is true if you have old leads/plugs and worn distributor, however with a squirt of WD40 on components in good condition they're fine, but clearly not as good as a Tdi in good condition.
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The best thing about the V8 though is the power delivery, 135 bhp seems pathetic - but it doesn't tell the story of how easy they are to drive off road. The torque delivery from tickover upwards gives it awesome capability in all conditions from rocks to mud becuase you can use a higher gear than in a diesel (e.g. 3rd low rather than 2nd low) which reduces wheelspin to maintain traction and forward progress.
I never bothered gassing mine though - I only do about 4000 miles a year and I want the loadspace in the back for recovery gear (and pies). Happy shopping anyway Andrew!