Jeff, 
I recommend staying with duals. I have run both single Webbers and dual
Dellortos (of course, the Dellortos provide me with much more power, due largely
to their largeness). One problem with the single setup is the distance the fuel
has to travel while suspended in the air between the carb and the head. The fuel
tends to precipate out and cling to the intake runner walls causing a lean mix
at low speeds and a suddenly rich one when you get up to speed and the air
velocity in the intake runner pulls all that precipitated gasoline into the
cylinders. That is why VW engineers used the dual carbs on the type IV's (before
FI). 
One other thing to consider. Why do you suppose that I'm about to ask you if
you'd like to unload your stock carbs, intakes, air filters, etc. on me? I have
a pair of nice Dellortos that I spent a pretty penny on, I can sync. them in
about 5 minutes by ear, they help tremendously in the power department, they
look cool, etc, etc. What could possibly be my motivation? I'm moving to
Milwaukee next month. They have annual smog inspections. Think my Dellortos have
a prayer of a chance of passing the visual inspection? They'll probably take me
straight to jail. Or lock me in stocks in the center of town.
Keep the Solex's. If you decide not to, I'll buy them from you. Seriously.
If you can't get in touch with me via E-mail (the movers were here today
threatening to take away my computer) it's because I'm in transit. I'll be
online 'till May 20, at phone number 809.722.7386 'till the 22nd. Then
unavailable 'til mid June. The e-mail will pile up, but I'll get it eventually.
One thing to say for the single carb... it's real easy to syncronize.

Andy McKinley
75112.2101@compuserve.com
'72 Westy, looking for a Thing to buy (and a complete intake, preheat hose to
heads for the Westy)