Its not a bad idea IMO. A guy on genvibe asked about this and got his arse flamed off almost. Of course I piped in and corrected many's incorrect ideas. They said he'd get worse mileage cause the motor would have to work 'too hard'.
The downside would be that the mounts probably don't line up and it would be a lot of work. Cost may be close to a wash after selling the parts. I'd really like to see what kind of results you'd get with it. Anyone got the numbers for the overseas duplicate compared with the 1.8?