Not a real big performance mod, but, what about this....
I had a Twin Cam back in the early 70s and in 93 my wife was looking a buying a Capri (new Convertable). I poped the bonnet and what did I see...an engine that looked very familiar..If a mazda 1600 DOHC is not a copy of a Lotus I don't know what is!
Even better there is an 1800 version of it.
The only problem I could see would be engine mounts (not to hard) and
Distributor (could be an issue).
Any thoughts???