http://www.fia.com/appendix-k-techni...ation-01012017
Above should be a link to latest FIA Appendix K regs .
As far as I can remember , [ without spending hours reading ] , for FIA historic classes your 205 GTI would have to be as per Homologation .
Before 1982 Group 2 regs allowed changing carbs for injection & the other way as well .
But for Group A I think you must use injection .
If you are entering for a National Historic series , then you will have to see what the regs allow , perhaps have a word with the series scrutineer .