Can't help you, but a couple of remarks. First, if your pre '64 is in any sense collectible, a swap to render it "only marginally so", pending "restoration". Otherwise, if whether simply non-collectible shooter or custom rifle, the alloy bottom metal, is typically a second choice. Softer metal, more scratch/aesthetic damage prone & considerably more difficult to ever refinish. All such as actual weight differential, negligible. Conversely, just to add that of the great amount of alloy bottom metals employed on more recent generations of rifles, that pre '64 alloy some of the best for comparative hardness & scratch resistance.
f I had a spare, I'd gladly trade for same condition 'real steel' bottom metal assembly about any day short of desecrating a collectible Featherweight!
Good luck!
Just my take.
Best & Keep Safe
John
