Interesting vehicle Jim. It's yours to decide on obviously, but if the vehicle has historical significance doing a particular specialised job it might be a shame to alter it from original, especially as a well sorted 2.25 engine can be reasonably quick. I have almost finished converting a 1968 109 SW to 200 Tdi, but it has no special past and will be my daily driver, purely because I prefer the look of an old Land Rover over a later 110. I will also need to tow regularly and the 2.25 diesel would have needed a total rebuild, so that's why I went the Tdi route.
Good luck with it, whatever you choose to do.
Daz