HMmmmmm (they need a better HMMMMmmmm face)
I wouldn't spend any money on the Old engine that won't fit on the new engine, Like I doubt Headers from the 1.6L will fit the 1.8L , but I think an Exhaust would be a safer bet. If your set on doing the swap I would save up the money for the swap, and make that your next mod, but if you wanna do some mods meantime, I would start w/ exhaust and then move on to suspension, or other things, as not to waste your money.
Hope it helps