postgres-pgtcl is only necessary for PG 6.5 (as noted in load-data-model.sql). Dump your database data, destroy it and reload load-data-model.sql from scratch and then read your dump back in.
The problem with that is that your sequences will be screwed up. You'll have to drop a bunch of them and recreate them according to your dump file (that has the right values). I don't know an easy way around that. Anyone ?