short answer is "yes you can". but ( there that word ) the 1100 motors have electronic ignition and 1000 motors have points. the gearing for the 1100 is different so you may gain or loose rpm at say 60mph
Medcoman if you are a GWRRA member I'd contact "Workbench" and see what Stu has to say about the "little things" detdrbuzzard mentioned. If you can shoe-horn a 350 Chevy into an Austin Mini, you can put a GL engine into a GL!