I want to fit 1.1:1 ratio rockers from a 1600 onto a 1200 (1385cc) engine. Will they bolt straight on ? Anything to be aware of ? Pushrod length o.k ?

Should be fine. They were fitted to later model 1200 but I'm unsure the year the swap happened. If you already have the 1600 rockers then hold one against the 1200 rocker and you'll be able to see the difference. IIRC the pushrod side will be shorter length to the rocker shaft for the 1.1 rocker.

Brian I have had them on my 65 1200 engine since I build it
they work great no problems fitting or using a little more eumph

just make sure you have the later style rocker studs not the old type that pull out easy they go into the combustion head area and are about 4 inch long you can see them easy on the under side of the head

Thanks . One head has old style studs, have been planning to get Boris to modify. Will fit later rockers then.