The usual replacement is an NG3 but I have heard of people using other NG series boxes. Our own jbcollier has a 395. JB feels that the 1st in too low and the gap between 1st and 2nd is too wide in the NG3 and I have no trouble believing it could be better. I have an NG3 and it doesn't bother me, but my motor (BDA) was built by the late Dave Bean and compared to his best 1600cc TC, it has a bit less torque till you get to 6000 rpm so that may be a contributory factor. Another factor is that I may not be sensitive or skilled enough to appreciate the difference.
I know that Spyder supports the NG3 and that would be a reason to go with one. You might check with them to see what other boxes they support. Richard at Banks would be another person to talk to about this (call him as he doesn't do email). He sells NG3s that are set up for the Europa. There are some modifications needed to do this (explained here:
http://www.greytower.com/jon/lotus/europa/gearbox/gearbox.html) in case you're interested in doing it yourself. NG3s went out of worldwide production in the early '90s (in South Africa) so parts are still available. The 365 that came with the 5 speed TCs, utilized custom parts so parts (especially the 5th gear) so some of those parts are either rare or unavailable.
Hopefully somebody who has more knowledge and knowledge about other options will chime in.
