Car stories....and I mean stories

Is this a test?

Changing the engine would have no effect on the speedo.

Changing the rear end gears would, but you said the donor car (Newport) had 2.76, but the GTX had 3.55.

Why would you change the rear end if the engine was blown?
He didn't. The speedo drive in the donor trans was geared for the 2.76 rear. When installed in front of the 3.55s it would make the speedo read way high.