Hi
I would say if you want a proper hard working tractor, the land rover axle would be the weak link, if the rest of the drive lines ok , after you have gone to all the trouble of designing/ finding or manufacturing parts and getting it to work

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From my experience of pricing out machine shop time, if you don't have the equipment and the general cost of parts these days, to do some projects I have thought about. You could be pretty close to the cost of original donor parts to put together a proper tractor.
Going that route would then guarantee it worked if the parts and tyre sizes matched up like roadless intended, and it would also mean that hard work should be 99% trouble free

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I don't think you can do this one off project on a 500 quid budget and a few cups of tea, and a bacon sandwich or 2 while figuring it out

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Anythings possible it's basically how much time and money you want to spend getting there the hard way

, then find it's not that great or totally useless at the finish

. You might get lucky first time, but I bet those dexta guys had issues the first time out and had to improve or re think during the first conversion

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If you steer clear of ebay and crazy auction prices, where guys can't or should keep their hands in there pockets and look around a bit, those parts/ or rougher 4 cyl tractors still turn up, if your not in a hurry
Thats my opinion on it from where i would stand if it was me, to be totally honest

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Regards Robert