Hi Russell
In Practical Sportsbikes July 2015, Alan Seeley fitted ST2 barrels to his 900SS, increasing capacity from 904 to 944 cc. His article explains what modifications were needed to convert the water jacket back to oil and to block off the coolant passages. There are pictures showing which coolant galleries have been plugged and where the oil galleries have been opened up.
If you'd like to see the article, PM me your email address and I'll send you a photo of the relevant pages.
If you want to learn more about what's involved, you could try contacting Alan Seeley direct for details:
alan.seeley@bauermedia.co.uk.
Hope that helps.