What speedometer gear/housing?

[80Grand_LeMans]

I for some reason lost the spedometer housing and gear from my transmission out of a 76 Cutlass. Its a th350 and has one that looks like this:

I'm not sure how to figure out what gear I need though. I noticed there's a difference in how many teeth the gear has, and also has to match the axle ratio and tires ](*,) . My 1980 Grand LeMans still has the stock 7.5 non posi in it. Also not sure where I could get one for cheap :-k Thanks for any help.

 

[SSedan64]

The BOP TH350 uses the same Speedo Housing & Gears as a TH400. The Chevy TH350 parts are different.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#400
http://www.chevellestuff.com/tech/speedo.htm

 

[80Grand_LeMans]

Thanks a lot! I wasn't sure why I could only find listings for th400 but it makes sense now. I'm going to just pull one from an olds at the junkyard and hope the teeth work with what I have.