Depends on the kind of tank you want:Something looking good on video but without real armor and weapons should be possible for 10k+ (open end, as for all alternatives)A tank that could take on a late WWI tank needs at least 6u201312mm of armor and at least one MG in a simple turret. Should be possible for less than 50k, if you prthe armament. The armor plates, simple sheet metal, can be cut and welded with tools auto mechanics usually have and use.A tank on par with WWII tanks like the T-34 would need real armor. Hardened steel between 45mm - 80mm is something you can neither cut nor weld using standard auto mechanic tools. To mount a gun comparable to the 76,2 mm main gun is not that easy. This task would need tools and skills you normally can not expect from auto mechanics. Somebody who builds and modifies heavy trucks might hav them. Expect a bill over more than a million for something usefull.If you want something that could survive on todays battlefields scrap your tractor as the only thing that you can take from it is the seat and maybee some switches. Make sure that you have a couple of hundred milion $ available for research and development and at least 10 milion $ for a prototype. Donu00b4t expect it to survive an encounter with something like an Abrams, Leopard (even I) or T90u2026