Well, I can't tell from the video. It is in a CCKW chassis, so originally it would have had a 270. It does not appear to have the sealed distributor the military 302s had,but that could have been changed. As far as I know the military 302s were the only gmc engines in that family that were not cast with a fuel pump on the side.

So it may be a 270 or smaller engine, or a 302 with a delco distributor.