Can I repair a body mount this way?

[WB72]

So my 67/72 project has a rusty rear cab mount. It isn't a write off, but the Center hole is rusting, so I was going to plan of a new piece. When I removed the rusty one, I was thinking about repairing it with a 1-1/2" washer on the under side. I would weld it in place to the good metal on the mount, is that a good idea? The hole in the washer is 1.61" while the hole on the good mounts are 1.50".

Will 0.100" make any difference on the rubber mounting hardware?

If I weld in the washer, is it better to weld it to the top, bottom, or the more work version of cutting the mount to the size of the washer and welding it in at the same height as the original.