when i first purchased my 300 ti Defender, I put in a 1.2 ratio transfer box as I mistakenly thought that it would improve the vehicles cruising ability.
I found that to be the case when going down hill, very pleasant!
A completely different story when approaching anything larger than a speed bump, it was horrendous, never away from changing down the box, struggling to gain momentum. On the few occasions that I tried towing, 3rd gear was the most I could ever manage!
My vehicle has an Allisport larger intercooler, modified pump and a variable vane turbo.
I took it out and replaced it with the standard gearing.
An overdrive is on the cards when funds allow.
I know that it is personal choice but I would recommend steering well clear of this option, especially where hills and towing is involved.
This conversion is fine for Td5 engines as they have lots more power available, not to mention tuning suitability.
Just my own opinion of course