Here’s a strong running 3.0 with a recent top end. $11K. Sell your core engine for $6k and be back on the road for another 100k miles. It’s complete so the removal /install could be done in a weekend with no special tools.
Read the reviews for GEX engines. They've been known for years to be crap. You would need to change quite a few parts to make a four cylinder work in your car. Induction, ignition, clutch flywheel, pressure plate, engine mounting, etc.