Thanks for the quick feedback. I guess I'll hook up the anti run-on valve first, although I have to get creative with the plumbing, as the effect created by the activated valve is to create a vacuum at the top end of the SU fuel bowles, thus counteracting the engine vacuum, which is trying to suck mixture into the combustion chamber. The Zenith carb had a separate vacuum line connection for that purpose, whereas I'll have to hook it up to the SU's overflow.
I may not do anything for the next couple of month, as winter is going to be around for a while (Toronto), unless the garage get's warm enough before that.
Assuming that there is carbon build-up in the combustion chambers, is there an easy wasy to remove it with solvent or similar, or does the head have to come off?