I am not familiar with later chassis, but, assuming your car is not a Big Seven, all the attachments for the rod brakes wil differ from 1935-37 cars.

Location: Auckland, NZ

The 39 chassis has a short brake cross shaft, so the bearing arrangement on the central stiffer is different, there is only one bearing housing located on the off side chassis rail, the nearside one is no longer fitted. There is also a small u shaped bracket on the rear cross member which houses a pivot for the brake rod back to the rear axle, and the ends of the cross member are subtly different in shape, being slightly more tapered. These are the only differences I am aware of, I would post pictures but recently I have been encountering all sorts of problems with Apple Phoro and photobucket so afraid that will not happen.

Location: NZ

the 39 ruby chassis differs subtly from earlier as mentioned above with only a half cross shaft and full girling brakes cable at the front and rod at the rear. the diff case differs as part of the rear pivot for the rear brake rods bolts directly to the diff housing as well.

Location: Pennines

Thank you every one! Very nice explanation and useful, i will pass these good infos.

Location: Italy

The last of the chassis used a back axle with stronger half-shafts, having longer hub tapers and different rear hubs to match. Also they had no locating dowels for the road wheels, which had simple holes for the studs instead of the keyhole arrangement.

Location: just north of Cambridge