1974 FG160 - Nut and Saddle Replacement

I've got just the info you're looking for right here.  yamahavintagefg.boards.net/thread/24/replacement-nuts-saddles  

The vintage Yamaha string spacings are notoriously tight. 

I increase the 1.36" spacing at the nut to 1.41" by replacing the nut with the TUSC PQ-6116-00.    You'll have to sand the bottom of the nut to get the nut action right.

For the saddle you can use any 1/8" uncompensated TUSC or bone saddle, although you may have to sand the width slightly to get it to fit, and sand the bottom to get the action where you want it.  Obviously you're going to have to drill a hole in the corner of the saddle pocket for the pickup wire.

You can widen the saddle string spacing by filing narrow notches into it.   I've been able to get the 1.97" saddle spacing up to 2-1/8", but it looks kind of weird.