The Saginaw has a fully-synchronized 1st. gear, so if it's grinding you've either got a bad blocker ring in the synchro, or the lube is too slippery. Try draining the transmission, run a solvent like mineral spirits or Diesel fuel for a few minutes, and refill with straight 90 weight or 85W-140. I had a similar problem with a Kawasaki motorcycle after adding some Kroil to the engine oil to free up the rings after years in storage- - - -the clutch started slipping! There was a common crankcase between the engine and the transmission, and the Kroil was causing the wet clutch to slip. A flush and refill solved the problem.
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!