Rebuilding an110r engine - a curly question

[skodakiwi]

I'm rebuilding an engine in a 1974 Skoda s110r coupe - the engine I have has a different rear crankshaft oil seal cover, to any of the other engines I have - looks to be a heavier design, quite a lot larger - I can't find any reference to this style in any of the factory manuals I have - was there a heavier racing engine built ? Or a superseded block design ? The block has been retooled to allow for the new cover

Engine number is 624085/12* - I note all the other engines are lower numbered (605695 and below) and have  /5* after the main number

Any input would be appreciated !

[Thefeliciahacker]

Imagine having a race spec skoda engine that would be mad