The early 280 SLs had the big fuel pump, later they got the small pump. The BBB has a section on retrofitting the small pump to cars originally equipped with the big pump. There is indeed a mounting adapter for the small pump, as Cees mentioned. However, the BBB does not say anything about changing the shroud, which leads me to wonder if the shroud remained the same throughout, with the adapter compensating for the different pumps. Need somebody with early and late cars to crawl under and compare them...
George Davis
'69 280 SL Euro manual