New engine for 5th gen Monte
#3
Yup, an L67 is the quickest way to getting some performance. Another way to go is to get an L36 and turbocharge it. The turbo can be costly, but you can make 400whp easily with a turbo 3800.
#6
I'm gonna say the supercharged 3800 also. You may be able to pick up a complete donor car on craigslist. GM put them in a bunch of cars. The Grand Prix, bonneville,a few models of buick and of course the 04 and 5 montes.
#8