Hi, I was having a little search for anything on custom trials machines and I stumbled across your thread, sorry if the issue is now dead and buried but I thought I'd share my opinion.
In the UK, trials competition demanded that the bikes are road legal as part of the rules of entry. This not only included lights and plates etc. but also a road legal tyre, something which may have dramatically affected the actual off-road potential of many bikes, but that's another story...
The gearing, as previously mentioned, is not conventional compared to road and 'speed' bikes, gears 1 through 3 are for use in competition, very short, but 4 + 5 (usually) are road gears, they are much taller and can actually pick up a fair pace, the jump between 3 + 4 is usually a very big leap so just adjusting the final drive gearing would not actually adress this. To be honest, I've always considered a trial bike (as is) for use here in London, loads of traffic, tight roads, loads of stopping and starting, getting to and from work without putting a foot down could be entertaining
When I found this thread, this Monty sprung to mind:
http://www.bikeexif.com/montesa