Actually, you could figure out how to modify the existing harness if you absolutely had to (already own it, no possibility to return), but Jess is right; you'll be better off with the correct harness, if there is one available.
Denny I agree. But I personally like to have a harnesses complete. But if you have some wiring skills you can make it look great and work! yes it is possible. It is easier to change some extras, like lights then the charging system sometimes... and sometimes I'm wrong too. Hope you had a great christmas!
its simple, make a 3 wire harness for generator to regulator (arm, fld, ground), take the 35 generator wire and connect to "bat" terminal on the regulator
Unless you get a custom wiring harness I would think the easiest approach would be to use the harness for the vehicle model year and just add the wiring required for the generator. It only involves a few additional wires like Kurt posted. You can purchase wiring that will match the wiring style of your harness.