I have been hoarding OEM syncros for a very long time. Attempting to burnish aftermarket junk to get them to work reliably isn`t anthing but a short life fix.
I have a dwindling supply of OEM moly syncros and their matching sliders,
and a good personal
supply of the best of the syncros the early 750/101/102/106 Original striated syncro rings and center grooved sliders that I only use on race gearsets. (with Redline 75-90 NS only) I would think they would still be used if Alfa wasn`t after cheap fixes to production cost.
The syncro dog assemblies from donor boxes from 4th/5th/ (and sometimes 3rd gear) are the source for the needed swap out to eliminate the unidirectional 1st gear syncro assembly, and most always 2 gears`s assembly as the teeth are blunted.
To insure that the replacement Dog tooth assembly has a long and smooth life
there are some modification to these parts that improve function.
If the internal surfaces of the syncro ring and the two friction bands are bead blasted to eliminate the polished surfaces that will improve the "gription" between them to syncronization.
If you feel the tip of the "used" syncro teeth`s points you can feel a burr on the top of good ones, and worn ones will have a spike upwards that enhibits the slider from engaging quickly, and worse pulls out on the syncro on disengagement. (Syncro failure!)
If you look closely at the syncro dogs in the pic you will see I have polished a small taper on the upper points outer part to chamfer and ease the sliders engagement.
I debated sharing this but what the hay...
As well the long standing problem of drilled gears and lube foaming has been long discussed.
I lighten differently than others. while syncro parts are off I backcut both sides of the gears heavily & the taper of the cuts have resolved that foaming issue.
Hope this helps...