So I'd like to hot rod out my new project, a 58 445 panel van. Its 100% torn down so I figure I'd replace the b16 with a b18. I'd like to build the b18 with an ipd street performance kit or something similar. Replace the cam, gears, valve springs etc. So my question is would dual 32/36 webers be overkill for a b18?

In case you decide to 'hot rod' the B18, I have a b18 race cam made by Volvo. It came in the rebuilt engine (never run) and I only ran it no more than 10 minutes deciding it was too much for my needs. Great price, if you are interested.

what I'm looking at buying are two misab intake mounts that bolt to the SU manifold.

Those would be the manifolds that look like a P-trap used by plumbers to install a sink? They'll work about as well. Garbage manifolds, and with the disaster that is the progressive Weber, a waste of time.
Pair of SU's is all you'll need.

"So my question is would dual 32/36 webers be overkill for a b18?"

In a word--yes. I worked out such a system on my warmed over B20 w/K cam, 11:1 compression, 44 intakes, port matching on the exhausts and cleaned up intake pockets.
Here's how it went---a fellow 140 driver with a much hotter motor than mine tried the 32/36 route using the twin manifold adaptors meant for B30 carbed motors. He gave up trying to jet them--always too rich, no matter what. I tried them on my motor with the same results. I then substituted a pair of Webers from a couple of Renault LeCars (30/30). Those took only a little fiddling with jets to get a nice smooth idle, very good throttle response and it could run right up to whatever I felt the redline should be that day--and 27-28 mpg on the highway. It also had a cool look--what with the slightly modified Triumph TR6 air filter housing I adapted. The motor looked like all CARBURETOR--like a Mercedes Benz 190SL of the late fifties.
The down side--high rpm vibration with all the manifold/carb weight hanging out there--first cracked an iron combo manifold and then an aluminum intake. It needed to have a manifold brace engineered in. I switched back to SU's because I had a good set and the SU's were what the car should have for its class in Time Trials.
I get the impression that the poster who responded first doesn't seem to like the 32/36 Weber. While it may not be the "hot" setup it is a trouble free, set it and forget it type deal. I've run them myself (singles) and installed them for clients. Both Ford (Pinto) and Chevy (Vega) used a Holley version. They each have real air filter housings with readily available filters. The Pinto version (not sure about the Vega) uses both electric and hot water to actuate the auto choke (my preference is for the Weber manual choke) which solves the indecision of the Weber electric choke (sometimes on when you don't want/need it). With the Weber electric choke I install a Chrysler ignition resistor for use in the winter months (slows the choke).
My 2 cents X 10 -- Dave

I rarely disagree with mcduck, but I've found that the 32/36 DGV can work very nicely on milder engines if set up tight. It doesn't necessarily come that way out of the box.

Oversimplifying a little bit, any carb setup is either adequate to support the amount of power an engine is capable of producing, and if it is, "more" carburetion gets you nothing at all and can be a liability in some cases. A single DGV will support about 135 HP, and you're not going to get as much as that without some pretty effective head porting. So yes, a dual DGV setup is indeed overkill.

I believe you're referring to Weber DG*V cabs= GARBAGE.
DCOEs are nice, though. 42s.