If the side of the transmission has a cast in T87, then you have the heavy duty three. You may have to clean an awful lot of grease and gunk to find out. Mac Van Pelt has a picture of the case on his website:
http://www.vanpeltsales.com/FH_web/F...D3spd-case.jpg. The light duty three looks like this, again from Mac Van Pelt's website:
http://www.vanpeltsales.com/FH_web/F...uck_3speed.jpg. The shift levers are also different, but I don't have pictures of each type.
Dick Webber is 100% correct, the color is vermilion. This was Ford's red color for only commercial vehicles for years.
I don't know if there is a year of truck or an assembly plant relation to the stamped vs cast badges. The other difference I have heard about is the 48s had ribs in the back of the cab, in front of the bed. I used to own a 48, but can't remember if it had this feature. Anyone have pictures?