QUOTE(einic @ Dec 17 2010, 06:32 AM)
Do anyone no were to by the base clip that glues to the front screen fixing the rear view mirror? It's a plastic "pad" that the mirror slides on to, mirror secured by one screw.
Can't find it in any web shops.
It sounds like you have a non-OE mirror there. As the others have stated, the OE mirror base is a metal trapezoid surface which mates to the glass with that double-sided foam adhesive pad you got (the correct OE mirror base attachment part).
So now you need to decide to either keep messing with an aftermarket mirror whose plastic part keeps breaking, or to buy a nice used or a new interior rear view mirror for your 914. IIRC that's the same mirror used on the period's 911/912 (or at least similar).
The last time I looked, they were still available new from Porsche & the usual suspects here (AA, PP, Pelican, GPR, TC'sGarage, etc. - all are dot-com's) but pricey - plus they regularly come up used in the classifieds here, 914club, ClubNARP.com, TheSamba, eBay, etc. if you want to to pay a bit less.
Get the part number from the 914 PET parts manual available for free download from the Porsche website, under their Classics section, so that you get the right part for your 914.