The differences there are between a RD and a RZ comes from they were not sold in the same country (at the same time).

 

	'80 > '82	'83	'84 >>>
EUROPE / BRAZIL	RD	RD	RD
CANADA / AUSTRALIA	RD	RZ	RZ
SOUTH AFRICA	RD	RD	RZ
USA	-	-	RZ
JAPAN	RZ	RZ	RZ

So differences can be:

-Only RZ or RD logo.

-Lateral reflector due to legislation (CANADA for example).

-Coloring for EUROPE vs USA, CANADA, JAPAN, AUSTRALIA / NEW ZEALAND.

 

RD	RZ
'83 EUROPE RD	CANADA / JAPAN / AUSTRALIA RZ
'84 EUROPE RD	CANADA RZ	USA RZ
'85 EUROPE RD	AUSTRALIA / SOUTH AFRICA RZ

-Catalyser system / power / weight for USA.