Most likely, you've got a fully-synchronized Saginaw 3-speed. It's a considerably stronger trans than the previous model, and it can be shifted into 1st. gear at any reasonable speed without coming to a full stop. I've run them in roundtrack race cars behind 400+ HP engines without problems.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!