[CR] Dropout Adapter?

Greetings:

I know we've discussed this, but...............are any of you familiar with an adapter to allow the use of a more readily-available derailleur on a Huret dropout? A Simplex SLJ 6600 fits perfectly, but the cage isn't long enough for my needs.

BTW: anyone out there know the maximum sprocket capacity of SLJ 5500 and of SLJ 6600?

Thanks,

Chris