My 48 Plymouth has a throttle body EFI, 3.9 V6, from a 1990 Dakota, mine has the 5 speed and 3:55 gears. (It actually has the full Dakota frame under it.) The car is fun to drive, it feels fast, even though it really isn't. I can get a chirp from the 235 x 75 x 15 radials through a good tight limited slip rear axle in 3rd gear! I get 17 mpg beating the crap out of it, and it will get over 20 on the highway if I can keep it around 70. When I blow this 3.9 up, there is another one waiting. Nothing wrong with the 3.9, they are tough, have decent power range, a will pull decent mileage. The only issue I see is there is little aftermarket support, as far as performance parts available. I am considering a turbocharger for the next 3.9, time will tell. Gene