I have a 2004 Trailblazer 4.2l I6. 2WD. LT(if it matters) I've had the TB for about 4 years now. I love it. But recently it started to knock and just progressed at a very fast rate. It's now making all kinds of squelling noises and just a loud knock that hits harder when I left off the gas. I've decided to sell my 05 R6 to pay for a swap in my TB. My TB has 147k miles. Regular maintenance. But after it started knocking I checked the oil and it was a couple quarts low. No signs of ANY leaking anywhere. Im wondering what would be the best way to go about it? What motors are a direct fit to my 04 TB? I should get about $3k fire my bike including extra stuff, would that be enough? I'm mechanically inclined and have changed the water pump, fan clutch, alternator, serpentine belt twice, oil changes, brakes, tire rotations, air filter changes, throttle body cleaning, spark plug changes (AC Delco), replaced 2 ignition coils, ect. Please help if you have ANY input for me.