[Berg]

I don't have any experience with the sonic turbo's but I can tell you that the old 400ci smallblock in my old black Malibu was a great little engine with plenty of power. You could swap in a healthy SBC chevy and keep all the accessories and mounts and not have to worry about modifying driveshafts or anything too. It is the cheapest way to go. An old performance rule was 1hp per cubic inch was a good baseline. I am a Big Block guy (hence the 454 in my current Chevelle and my Suburban I use for towing) but I wouldn't rule out a healthy streetable mouse motor. Doing a big block swap correctly costs a lot more than some people realize. For starters, you are going to want to upgrade your front springs and sway bar at the least, most likely add a rear sway bar and boxed control arms- and throw enough HP and torque at the 10 bolt rear and see what kind of carnage you get. IMO anything around 400hp and over and I'd be running a 12 bolt or a Dana 60 or 9" F**d rear. That alone is going to require fabrication to put a non GM axle in if you can't score a good deal on a 12B. Don't forget you'll need a new radiator and fan shroud and accessory brackets for your power steering and alternator. You now have my .02 )