I've got a 1986 Chevy half ton van, overdrive auto transmission. Only
50,000km on it (35,000 miles). I've had this van for 10+ years. The carb has
always been an issue. Fuel leaks around the throttle body, questionable
choke operation, random flooding, etc.  There was also a brief carb fire
after an incompetent mechanic screwed up the fuel line.

I've been keeping an eye open at the auto wreckers for another truck to come
in with the same carb, but no such luck. I'm sure that my carb is a
Rochester part 17086044 or 17086048. The eBay carb is a 17085226 and it
looks like it was very recently rebuilt.

I did find a carb on eBay and upon arrival it looked VERY good. I thought it
was a good match for my van as well.

I went to swap the carbs around today and found that they aren't very
similar at all. They are both M4MED carbs, but the vacuum parts are layed
out much differently.

I've posted some photos and diagrams at http://members.shaw.ca/linkto/carb.
Apologies for the quality. These are cellphone photos.

On my van, the rear secondary break vacuum line goes to a "VAC TVS" (temp
sensor?) on the air cleaner, then to the manifold vacuum. The eBay carb
looks like this line went straight to manifold vacuum.

My van has a primary break assembly, but there is none on the eBay carb.

At the top, rear of the eBay carb there is a vacuum pipe. This pipe doesn't
exist on my carb.

On my carb there is a vacuum controlled "throttle kicker". The eBay carb has
an electric solenoid here. The cams on the throttle of each carb are
different shapes so these parts can't be interchanged.

At this point I don't know what to do. I don't want to tear down the eBay
carb to start swapping parts around. That's the reason I don't trust my
current carb. I don't see any way to get the eBay carb to work in my van.

What should I be doing? Would it be wise to just take both carbs to a
rebuilder and ask for one good rebuild? Would I be better of with a new
replacement Holley, Rochester or Edelbrock? Am I looking at a lot of cash
for this?

If it makes a difference, I'm located in Calgary, AB, Canada.