Thanks All - had to procede before the link came in - rain and all....

Snapped a breather screw as I now read - common - will have to order one from MB..$4 eh...!
Went with RTV as suspected, since its a low pressure low temp app - little risk on choice. Loctite - what a bugger to squeeze out of the tube!...painful.

Love someons idea of running the covers through the dishwasher!...checked with wifey....ha!

Got the air filters on just as it began spitting.

I'll Leave her over night before I give her a run up.

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It appears the cover is magnesium - did some research - most probably RZ5 94%Mg (Magnesium), 0.5% Zr (zircon), 4% Zn (Zinc), rare earths approx. 1%.
Be good to get confirmation on this.
As for finishing and removing/disguising all the casting defects - maybe a sand blast would provide the best results and then a satin laquer, rather than painting - personal choice though.