Overdrive vs High ratio kit?

Ok, problems with gearing in my SII 200TDi conversion (subject of comments on the thread "PTO take offs"), I've just had the very nice girl from Ashcroft's phone me up to say they've a high ratio transfer gear kit in stock @ £255 + vat and carriage, brilliant....but, I've already bought a Fairey overdrive, stripped it, replaced the needle roller bearings and seals, so it's sitting ready to be fitted?
My question is:-
What's the high ratio kit like to drive??
I was thinking of the overdrive "AND" 3.54 ratio diffs, (I've driven another SII with 200TDi and an overdrive, and it was still screaming it's head off at 60mph?),
but will the high ratio transfer gears and 3.54's be too much at the bottom end?
Anybody got any experience of mucking around with these components?
My overdrive would sell, and might even pay for the Ashcroft kit?
I'm hoping to take the Landy to southern Italy at the beginning of next year, so getting the gearing right, might make a more pleasant journey??
Any help gratefully appreciated?
Ken.

if it was me i'd go the HR geared route, they'll be a lot lot more robust that any OD and you wont have any issues fitting the PTO

and selling the OD will easily pay Ashcrofts bill

The only issue i have found with 3.54 diffs in a series is they can sometimes be too quick in low box. not so bad with a diesel cos of the high compression but with a petrol they can run away very fast. Depends what you intend using it for but i reckon the HR kit will be better than the overdrive.
Having said that its worth trying both perhaps and if you dont like one or the other sell it!
I dont know if the low ratio would stay the same with the HR kit, i presume it would just like all LT230 transfer boxes do, irrespective of the high box ratio.