I have a TH400 from a 70's B or C body that drives the speedo from the front wheel. I'n installing it in my '68 442 which obviously has the traditional setup.

How much grief would I have converting it, or would it just be easier to install an electric speedometer? I'm leaning towards the speedo fix...

 

No, you have a trans from a 1966-1970 Olds full size. 1970 was the last year for the wheel-driven speedo.

You have several problems here. First, these transmissions could have come with the hole for the speedo cable adapter plugged with a sheet metal plug, or not machined at all. If the latter, you cannot convert without major work.

Second, the TH400 from the full size cars use a longer tailhousing and output shaft than those for A-body cars. If you install this trans in a 68 442, you will need to have your driveshaft shortened to fit.

Sell this trans and get the right one for your car.

 

Sorry, bad memory... thought I remembered these were a little later.

I have a short shaft and extension for the trans, so the driveshaft should be ok. The hole is plugged with the sheet metal plug.

 

So you're prepared to completely disassemble and rebuild the trans then, as the output shaft is the last thing out of the case and the first thin into the case, right?

In any case (pun only slightly intended), if you have the short output shaft, it should have a speed drive gear on it. Knock out the metal plug and the speedo cable adapter from a normal TH400 should fit right in.