Sierra looks just like a normal 4spd escort box with an extra alloy spacer between the cast iron gear case and the alloy extention housing (circled in red below) and a different shifter fitting (three bolts instead of 40-odd mm screw fitting);

Two most common Toyota boxed fitted to Escorts - firsdt is a T50, second is a W50;

Hoe this helps you identify your mystery box....
Cheers
James