Go new if you can but expect 2000 or a little over when all said and done with the linkage, manifold, carbs and all the Jets and venturies to get them dialed in. You can get a good set of used out there but you might have to rebuild them. Not hard job but does add to the cost. With used you might find some perfectly jetted for your set up but the odds are not in you favor so you will probably have to spend some $ on jets ect.
I have O E Rs on my car from http://www.piercemanifolds.com and they have been great. They can get the jetting and venturies very close if you give them all the motor info.
Go with a set of 45mm and use small venturies if your motor is stock. As you modify your motor you can change the carb internals to match, the 45s will handle a cammed up 3.2. You will be limited with a set of 40s.