Warning: not a truck question.

Ok, my 88 tbird has a sefi 3.8 auto. On a whim, would a 4.2 drop in its place?

What's the gas mileage comparison between these two?

Secondly, the 3.8 has been rebuilt just before I bought the car(50,000 miles ago), and now the aod is starting to slip. I had plans to fix up the tbird with a big v8, but I would like to find something the 3.8 could drop into, hate to waste a good engine. Any ideas? It would be a daily driver. (even a pinto is sounding good, so far)

 

It will bolt up to the tranny but I'm not sure of the motor mount arrangement and the 3.8 intake won't fit. Also you will prob have to fabricate some accessory brackets to make everything work.