Very good German website about the R20 and R30 (easy to translate with the http://translate.google.com/ ):

+++ http://www.renault20.de/Index.htm +++

Because it isn't possible to paste direct link to every subpage, for faster access I'll rewrite here the factory codes:

Typ-Nr:
[R1271] - 1976-81_______- R20 L/TL/GTL

[R1272] - 1977(MY78)-80 - R20 TS*
[R1272] - 1979-80_______- R20 LS
[R1277] - 1980(MY81)-82 - R20 TS/LS*

[R1276] - 1980-84_______- R20 TD/GTD

[R1279] - 1981-84_______- R20 TX
_______________________________________________________________________

[R1270] - 1981(MY82)-84 - R20 TurboD & R30 TurboD*
_______________________________________________________________________

[R1273] - 1975(MY76)-76 - R30 TS*
[R1275] - 1976-81_______- R30 TS
[R1278] - 1979-84_______- R30 TX


*In brackets I've added Model Years, that we use on the site, as some years mentioned by this table indicate start of the production only.
For example in case of the "R20 TS/LS R1277" our model year is 1981, what isn't illogical, if we compare trim differences between the cars from these years.
Similar is with the "TurboD". Despite the table is saying "1981", then in text the site explains, that it was available since 1982.