Filling A Small Hole In A Cast Iron Caliper Body and Remote Bleed Nipples???

[Duk]

For my rear brake upgrade in my 75, I'm using series 4/5 Mazda RX7 Turbo calipers (they have an internal handbrake mechanism, fit over a 20mm thick vented disc and at least twice the pad surface area of the original Alfa calipers).

Now the Mazda calipers are a little strange in that they have 2 bleed nipples. 1 of these nipples and its associated threaded boss needed to be removed/ground down so I could make them fit close to the diff housing on the transaxle (rest easy, the other nipple is at the highest point for bleeding air).

So I need to be able to safely and reliably fill this small spare hole in each caliper. Welding it with a cast iron filler rod is pretty obvious, but would brazing or silver soldering be strong enough to do the job? Both of those would be much less involved than welding cast iron.

And while I'm talking calipers and given that the remaining bleed nipple will an absolute prick to get too, being able to add small hoses and use remote bleed nipples would be enormously helpful! Has anybody ever seen such a thing applied to brake calipers?