I've done it with my 1973.5 It was not that difficult. 3.2 is a great engine, and Motronic was a lot simpler to set up than the cis. There are a few issues with the 3.2 engine. They used the dilavar studs which can break, and ususaly will need the original valve guides replaced. Transmission issues are minor, notches would need to be cut in the housing to clear the flywheel sensors on the 3.2.
1973 Porsche 911 - YouTube