Is there any advantage to running a monojet or varijet carb instead of a B or BC carb on a 235?

If you have a varijet stick it on the shelf as a conversation piece. I started working in the generals trenches in 1980 and these were and still are a pile, IMHO. The monojet has throttle controlled metering rods as opposed to the vacuum controled power system on the "B'. I have never run a mono-jet on anything other than a 'modern' chev 6. I am running a "B" off a 1967 C60 292 on my '60 C10 235. Do a search (I'm not able it seems), there is a good post with all the model "B" info you could want.
292 had the biggest throttle & venturi size, 1967 was the last year for the "B", replaced by the mono-jet in 1968. Did I mention I'd go with the "B"?

p.s. If you haven't already, think about putting HEI on that 235.

The mono-jet has a vacuum controlled metering rod,in the same order as a Q-jet. I have played around with the power piston spring on a 1972 model while running it on a '69 230. I have not run a mono on anything other than a 193-292 series motor either, but see no problem if rebopped per Doug Roe's Rochester book explains. I do believe that the 292s had a big 1-11/16 butterfly and 1-5/8 venturi in a mono version also. And the mono-jets dont make that wimpy whistle noise at part throttle accelleration.

The varijet would be neat if you could make them work right as the design, in principle, is like that of english SUs. But I too never had enough interest to bother one.