The parts book says that the pedal boxes are the same. However, there are early and late versions. Which version is correct will depend on the chassis number.
Spiders up to chassis #1495.04255 have the early version; part #1365.66.711.
Spiders from 1495.04255 got #1365.66.741, the late version.
There is a difference in some of the pedal boxes - see picture - I think it's early & late, but it may also be disc vs drum brakes as the master cylinder's were different, 7/8 for discs vs 1" for drums.
Yes, I still need a box! The pictures that Greig posted help alot Thanks! I believe it was the 36mm one for drum brakes!
I checked and my spare is 36-37mm. So it sounds like what you need. The brake shaft moves freely in the bushing. The clutch shaft will need lubricated at least, and possibly rebushed. Email me at firstname.lastname@example.org and we can work out a very reasonable deal!
I'll be gone racing through the weekend and at a meeting all next week, so I probably won't be able to send it to you until the end of next week.