Speedo Cable

[theaddictedchef]

Hi guys....
Still plugging along and should have the new engine in at some point before dark. 
I need some sort of speedo adapter.   My tires are bigger and I've paced my speed and seem to be 30% off on my speedometer.   
Is there any adapter that I can get to account for this?  New speedo cable?  I'm in Phoenix so would like to physically pick it up and install while the engine is out. 
Thank you!

[LTZ C20]

Just have to use different color/ratio speedo drive or driven gears in the tail shaft of your trans.

[rich weyand]

If that's a K truck, the speedo cable came off the transfer case.  The transfer case didn't have the zillion gear combinations of the TH350.  New from the factory, they came with geared speedo adapters.  NOS ones are expensive.

But if you figure out exactly how far off it is, you can order an adapter from a couple different places.  Be careful to get the correct mating pieces: little male-male or male-female inserts that connect things together.

http://www.texasindustrialelectric.com/speedo.asp
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

[LTZ C20]

Yea, 4x4 is a tad more tricky.  Forgot to mention as rich did, 4x4 cables come out of the transfer case.