[Legbreaker]

My thoughts are that the 105mm armed LAV would not have been sent to China as by the time it was developed, that conflict was effectively won and lost.
HOWEVER, it's certainly conceivable that a number of LAV-75 were modified in country to fit missile launchers, either in a box such as the Bradley, or rail mount such as BMP. The Dragon (or Chinese version) mount would be another relatively common modification.

By the time the M-20 was ready for production the US army would be in need of all of them (with a few maybe going to the marines). This is not to say a few prototype M-20s weren't sent to China for testing, but I'd think they would be very few and far between.

Hmm, According to the "Authorised Levels of Principal Combat Vehicles & Weapons" on pages 17-20 of the 1st ed US Army Vehicle Guide, 392 LAV-75s were required to fit out units with the vehicle assigned to them. I would estimate an actual production run of around 450 would have been desired to provide training vehicles and a few replacements.

If production was commenced early enough (mid to late 80's) virtually the entire order may have been produced before the war. Perhaps the 105mm was already on the drawing board when the Soviet/China war broke out and so those vehicles sent to China were already several years old and due for upgrading anyway?

If however the production run was delayed until a year or two before hostilities, production is likely to have been much less, with a substantial proportion rolling out of the factories and directly onto ships bound for China.

Of course we've nothing in canon I can see that states any LAVs were sent, so it might well be that US units went to war with the LAV-75 and upgraded peicemeal in the field....

Further reading of the US vehicle guide reveals a total of 68 LAV-75s still operational (or at least on the books). Some of these vehicles are in the hands of units never offically assigned them (such as the 8th ID). Obviously there may also be a few in enemy hands, or not "on the books" for any number of reasons.