Of all the laundry list of things you can do to advance your 401 performance, I'd offer that 'linkage replate' is way down at the bottom.
Plinth, yes, as it will absorb and transfer outward the motor and mechanical vibes you don't want headed into the pickup, but -- that's just the thing. Even the plinth is itself a little down the list, from the main two categories.
Those are, tied for first place, drive-motor rotorshaft, bearings and alignment, and spindle-bearing, journals and thrustpad.
No coincidence that these are the two places where wear-&-tear are felt most accutely on the 3/401. Everything else comes after these two. Even the very-important category of compliant elements, bushings, springmounts, etc-- should be viewed as being at the service of an already well-attended set of drive mechanisms. Also the plinth, which is very-important, should be notched in as a support of the drive movers.
Maybe it doesn't seem too significant if one is attempting the "total rebuild", but understanding the flowchart of important restoration categories is critical to understanding the machine. The foundation of the house needs to be comprehensively inspected (and perhaps restored first) long before the nice new doorknobs are installed upstairs.
Okay, rant segment over.
Continuing good luck on the restoration.