There used to be a drilled steel coverplate for Mafac racers to stiffen the pivot mounts. This, combined with bronze bushings , eliminated the tendency for squealing anfd gave much greater power as the pivots did not flex. I don't remember who made these but I seem to recall them from around 1978. the mid '60's Mafac Tigers and Top 63's had much beefier arms and pad mounts and were quite a bit stronger than Mafac Racers. The early racers were stamped with just Mafac on the front arm. I have a pair on an old Jack Taylor women's model frame that I just got, and they're also on A Rochet that I'm hoping to buy. Making a custom pivot stiffener for Mafac's is relatively easy to do. It doesn't take a very thick piece of material to provide additional rigidity to the pivots. Aluminum and stainless are both readily.
I don't see many advantages for a brazed on centerpull over an inhanced Racer, stopping power is very similar.
Santa Rosa, CA