Hi Moonpup,
Just read your response in General Discussion,Nos 175 Barrels, but will rely in 350 Talk.
I am aware of the real variations in the barrel castings for the 350. You may remember, I 'didn't tread on your toes', in a follow up topic as below where we had a long discussion on this very subject (Was 12 months ago). :-
http://bridgestonemotorcycleparts.com/index.php?topic=3159.0Referring back to the original link in your post, have a look at photos 4 & 5 . :-
http://bridgestonemotorcycleparts.com/index.php?topic=2822.0What you see is a l/h barrel on top of another l/h barrel, they will look different because of the front to back taper on these parts, they are not symmetrical . Analogy - put your L hand on top of your R hand in front of you, palms together. They don't match, turn one hand round and they do. To do a true shape comparison, you need a left and a right hand barrel placed on each other. It was only some time afterwards that I realised the oversight in Steve's post. ( I have checked with him that he is OK with me saying this).
So, I believe we can rule out any significant change in the barrel/head
profile shapes for the 350. OK, there maybe some very minor shape variations between the shapes cast by different suppliers, (possibly 2 or even 3?).
The above does not help in sorting out the known 5 barrel variations, you identified but it does exclude another possible complication for anyone trying to get a matching pair.
I now have 3 GTR engines, an early one,-879 and 2 later - 6052, 6868. When I've got them stripped down I'll make a tracing of each of the head shapes to see if there is any difference and post the findings.
Regards, Brian the Brit.