I have an 84 K20 that currently has a th350/np205 set up. The trans is bad so I'm looking for a 400. My questions are; What mods will needed to be done? If it bolts right up will I need to get an adapter for the tans case? Would I have to make any changes to the drive shaft or the trans. itself? What about gearing? How do I know what spline my 350 is with out taking the trans off? I have never delt with transmissions before. If anybody can give me some advice it would be great.. Thanks in advance.