BritishInvasion -
A few years ago someone was selling one on ebay with a Kubota diesel engine in it. This is an EXAMPLE, I don't know which Kubota engine it was, but 25 HP sounds right :
KUBOTA D1005 DIESEL ENGINE 3 CYLINDER 1.0 LITTER NEW 25HP MEETS TIER 4 NICE | eBay
Ha ha, here is a Triumph with a Datsun B210 engine :
Triumph : Spitfire Triumph : Spitfire | eBay
CarloSW2