H22A7 swap....best bang for buck. Use the ATR gearbox, and an M factory shorter final drive. Ive done a couple of H22 MB's, felt really good to drive. K20 is do-able and Ive done that too but the jump in cost is massive, your talking going from 3500 for a drive in-drive out H22A7 swap to double that for a basic standard K20....