Rollins240z

I searched and need some help changing my speedometer gear. 280z 5 speed tranny. 300zx turbo clsd 3.7 diff So I bought an 18 tooth “blue” speedo gear to match the ratio of my diff for an accurate speedometer reading. I went to change it out and install new O rings and pulled out a purple 21 tooth gear. The teeth part of the 21 teeth purple gear is larger in diameter than the blue 18 tooth gear I’m trying to swap out. I did some research and my understanding is that the 20-23 teeth speedo gears use a different housing for the correct angle of the larger sized tooth gear offset. Here is the link http://www.classiczcars.com/applications/core/interface/file/attachment.php?id=1652 The 18 tooth gear shaft fits my housing perfectly, the only difference is the number of teeth and the diameter of the teeth. Do I need a different housing for my 18 tooth gear or am I ok? Z is not running so I can’t test it yet. I also read somewhere that the housing can be turned slightly to accommodate the smaller gear teeth size.