You should be able to remove the electronic speed sensor and drop your cable driven one right in. As for gears, use this:
http://www.tciauto.com/Products/Tech...eedo_gears.asp
If the converter you have is non-lockup, you don't need that square plug at all. Best bet is to cover it up so that it doesn't fill with crap so you can still use it easily if you swap a lockup converter in.
- Justin