There are various wheel and tire sizes for 100,200,300 and SP. I have no experience on -400. The classic wheels are all physically interchangeable but can be different sizes. Early SP aircraft were odd in that the nosewheels were bigger than the mains. Other differences in the nose gears were minor such as some having micro switches in the gear system,others having prox switches or a mix of the two. While not 100% certain I believe the nosegear assembly would be interchangeable between all classics.If the aircraft was not to be flown wheel sizes could be all the same - some wheels the same size are not legally interchangeable due to some 747s being certified at a higher gross weight.