https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/10481336/gonew/1/WTS:_Pre_'64_Winchester_M/70_B#UNREAD
Not sure this helps: bottom metal for a pre-64. It might depend on what you are using it for. I tried swapping out the bottom metal from a pre-64 featherweight I own onto a New Haven Classic Super Grade. The trigger guard wouldn't fit over the trigger of the newer rifle as the trigger is too wide. You might want to check it out before you buy.
Good luck.
