Speedometer Question

[67 GTX]

My 67 gtx came with a 150mph speedometer. The belvedere's came with the same speedo, but a 120mph instead.

What I am trying to figure out is if there is any physical difference between the 120 and 150 speedos. The magnets and the cups for each seem to be the same size.

I tested both with a constant speed electric drill, and they seemed to read about the same speed.

From what I can gather, these should interswap?

 

[SDCoronet]

Just my 2 cents based on what I have read over the years:

I believe that they will swap just fine. I also believe that the only real difference between the 120/150 mph speedos is that the internals are magnetized differently.

Let us know how it works and post lots of pics!

 

[67 GTX]

I found out that they do swap, as the only difference is the different magnetization and slightly different hair spring.

I'm having a 120 that I have (in better shape) converted from the internals of my 150 (rusted).