Yet another problem!

[4x4man09]

On my 73 C20 the tailgate wont latch closed. You can close it, but if you pull hard enough it will open. We bought a used tailgate and tried to put that on, it also does the same thing. Another thing is the hinges. When we put the other tailgate on and you try and close it they hit the inside of the tailgate. If you unlatch them it will close all the way but wont latch. Why is this happening! We just wasted 50 bucks and had no luck!