any one of the above words can be taken but it is not necessary that every word should be translated into pure targer language. Popular words can be taken or adopted into target language. Here for 'seat' we can use seat in devanagari script.

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Note added at 46 mins (2004-12-04 18:20:33 GMT)
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souch ka seat my please be corrected as \'souch kI seat\'

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Note added at 1 hr 1 min (2004-12-04 18:35:18 GMT)
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The answers were given in singular you may pl. make them plural.

Seat has become part and parcel of Hindi and there appears to be no need to translate the same as it is fully competent of conveying the implied meaning even to a layman.

And your sentence may be translated as:

YahA(n) 80 say adhik shauchAlya khand (or block itself) hai(n), jinme(n) lagbhag 660 seete(n) hai(n)

there are basic difference between western and indian conception of lavatory.in any hotel in india,there are provision for indian style and western style(comode) of toilet.if the question indicates western,then 'seat' is correct but if it is for indian then the sentence is:
Lagbhag 660 souchaasan yukt 80 se adhik souchaalay haain.
we can use 'souchaalay ki ikaai' or simple 'souchaalay' for toilet blocks.
we can also use