The best barrels I have found come from http://screamingroo.com/online-store/47mm-barrel/
But I'm in OZ.
I will not use any other barrel I have been able to get here.
Don't know if this helps?
They have the larger ports, larger fins, 40mm inlet stud spacing, correct deck height for 40mm stroke and excellent port timing.
The transfers need a tidy, but he does also sell a barrel that has had a little work done to it already.http://screamingroo.com/online-store/roo-66-performance-barrel-kit/.
Best quality parts I can find.