Do B&S engine series numbers relate to ft.lbs of torque, ie: a 550 series has 5.5 ft.lbs?
Correct; that's B&S' current series numbering system. Introduced around 2007 I believe, to replace the horsepower ratings they had used for a long time prior.
It would be interesting to know whether the supplier has other models available - probably based on other aluminium extrusion shapes - that could be useful for bringing various vintage engines back to life.
Grumpy, that carby in bigted's fleaBay link is actually a pretty faithful repro of the OEM unit. It used that alloy extrusion too, which seems to have been exclusive to the Vector series. That seller has a fair few repro carbies listed, mostly Tecumseh and motorcycle types.
The Vector series had its own service manual, which also covers these carbies. The Tecumseh general Tech Handbook, and Carburetor, manuals don't cover them.
