T520 because optional 1080p panel or X220 because smol, don't see much point in the T420 but those are often cheaper than the formers. If you don't care about cpu at all any will do, a T61 or T60 is fine, anything really.
>>11897155You can swap a xx20 keyboard on some xx30 memepads, I don't remember if you need to mod something else though.
