There are really no 1/32 helo crew figures. 1/35 is close enough to work though. I use them in 1/32 helos all the time.
A good plastic Vietnam crew is by Dragon. It comes with two pilots and two door gunners. There is an issue though, there is only one M23-doorgun mount (as used on Hueys) included. You will either have to get two sets, or purchase an AM doorgun set from either Cobra Company or Bravo-6, both in resin.
Bravo-6 also does very nice pilots and door gunners in resin. They are quite expensive though.
They also offer just the gun mounts and the gunners w/out guns as seperate kits too.
Cobra Company M-23 Doorgun set:
http://www.cobracompany.com/35017.htm
Here are a bunch of other options (some more modern) as well.
http://aeroscale.kitmaker.net/modules.php?op=modload&name=SquawkBox&file=index&req=viewtopic&topic_id=230821&page=1
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