Not fast enough? Weird thing to say.
As far as swapping, sure. IF you want to do tons of fabwork and whatnot. You'll need a donor car (not just the 3.8) to grab the entire front end out of, assuming the Lumina has a spacious enough bay for you to be comfortable with.
The 3.8s are nearly bulletproof. I'd opt for a 3.8 over a 3.4DOHC for only durability; I'll happily (and have almost done) swap my 3100 for a 3.4DOHC.