You will find most of the responses here are mostly negative to chop or bob a Triumph even thought it was very popular back in the day and that Triumphs were possibly the best to do it with. Even as a show and polish bike today they are not very popular and don't have much value but cost you an arm and a leg to build.
If you want to cruse the highway at 85 - 100mph your best bet IMHO is to get yourself a BMW Airhead they can be picked up dirt cheap, they run forever and they are all metric sized, very simple to change and modify. They BMW nut will go nuts for doing that, but turning them into cafe' racers and bobber’s and rat bikes attract large crowds and followers and believe it or not higher value than the original bikes.
Today the value of some triumph's just keep on going up and some part are like chickens teeth and you will pay top dollar for original parts especially pre units. A front fender can cost as much as $800 and a gas tank as much as $1000. See what this tank almost went for http://www.ebay.com/itm/261128193081...84.m1438.l2648
ebay listing 261128193081
Now what would the value be in a few years when most people today are trying to restore back to original?