I lived at 22nd St. and 9th Ave from 1978 - 1983 so Stuyvesant was my LBS. It was on 14th near the corner of 9th Ave. It is now most definitely gone. You can check the street view on Google maps.
The location was where the scaffolding is now.
It occupied 2 storefronts. The major brands sold then were Atala, Scapin and Guerciotti. There were bikes of every description with the Corso label (the house brand) . Also many unpainted and/or unbranded Italian frames of all sorts - form gas pipe to Columbus SL. I bought bits a pieces there including, most memorably, a beautiful pair for Maressi "Top" shoes. All leather. inside and out w/ nylon soles.
At some point in the 90's they cut it down to one storefront, then it became A Bike Shop, then it disappeared.
The A bike Shop has an interesting connection because the Shop on Avenue A was in existence in 1989 while Suyvesant still existed on 14th. One of the major wrenches at Stuyvesant was a Cuevas (Francisco?). When my Colnago needed a repaint I went to Stuyvesant. I was "steered" to A Bike Shop where I met Andres Cuevas , who did the repaint. This was the red and black Colnago Arabesque that was semi-lately owned by Mark "Torpado" Agree of this list and MI. Now it's out there somewhere.
When exactly the 14th St. store became A Bike I don't know.
As far as Toga goes, there was one store back in those days - 10th Ave around 51st St.
Julian Shapiro
Sag Harbor (100 miles east) NY