You might try to download manual of both cars from AE web sites if you want more detail. Don't forget that the axle/3 holes hubs are not cheap. IRS differential set is ~$38 at tower hobbies. The blue aluminium screw set is about $9.

BTW I just bought a used hybrid 12LC/12L3 yesterday. It come with what I think 12LC chassis and the 3 holes hub. Not at very good price (~70) but I just want it for spare parts which will cost me more if order them seperately. I have to stock part by my own because they're very hard to find here (I'm not living in USA).