The only Dyanes fitted with 200mm drums were those with the 435cc engine.
Marketed as AYA 2 (Series A and AM ) from March 1968 onwards, so that should be the same gearbox as used in 2CV4s; lower ratios overall and identifiable by having 2 rings engraved on the input shaft...

In France, they're rather fond of 'mixing and matching' parts without too much regard for the consequences, in my experience.
One of my customers bought himself a 2CV from France which turned to have a 2CV4 gearbox mated to a 602 engine, another managed to buy an Acadiane with friction damper front arms and axle fitted.
The fellow who'd 'restored' the Acadiane claimed to have broken 3 Acadianes to get the best bits, guess he got confused with the pile of parts he'd assembled; to cap it all, having the wrong fluid in the brake system made Brian's journey from the middle of France back to Harrogate rather 'interesting'.

The only Dyanes fitted with 200mm drums were those with the 435cc engine.

Thanks Ken. Yes I wondered about the mix-and-matching. Would the 435cc AYA 2 model gearboxes have had the same clutch arrangement as the M28 engined varieties too? ]

My gearbox has the overhead clutch fork ('modified' cable connection too) and the lever at the back of the box. If it does have the lower ratios I guess it may help with some of the inclines around here?