Frustrated with Airbox

Airbox for my 1983 KZ750K Twin . I pulled the tank, carbs, and carb holders off the motor, but I STILL cannot get this damn airbox in. I'm really hoping I haven't purchased the wrong airbox. Am I going about this wrong? It seems like it is too long and I'm fighting the intake on the motor and the frame to even somewhat squeeze this in, and even then I can't press it in. 

So my questions are as follows

What is the major difference between the airboxes, how can I identify the exact one I have?

How the hell do I get this airbox in if it is correct?

There is a reason people tend to convert to pods, and your situation is a prime example, not that I recommend it. Maybe send pictures of your problem and we can go from there? I know it can be a pain in the trunk. does your airbox look like this? The image may not help. There should be a serial number on the airbox somewhere. If it has one, could you share it?

Sadly at work at the moment. I do have the numbers written on the airbox though 

KHI A 014