Triumph made and catalogued a bolt on hardtail for flat track racing. Prior to 1970, rigid frame flattrackers were the way to go and I recently saw some of these for sale. I am pretty sure they were NOS, because the supply was limited and the ad was in the AHRMA newsletter, Vintage Views. The ad should be on their AHRMA mart page on the AHRMA website @
www.AHRMA.org This would make for a better handling bike, as most "chopper" hardtails are designed to be used with a raked or extended front end. Just save the swingarm and shocks, when the hardtail beats your kidneys into pulp, you can bolt the rear suspension back on!