The guys on the T nation combat forum would probably be able to give better advice and also look through there training logs as some use 5/3/1. In saying that I would have thought 2 days a week full body is the best option if boxing is your focus.
I read on the combat subforum that the priorities should be skills training, conditioning and strength training in that order. Training 4 days a week strength isn't going to make you a better boxer compared to 2 days a week and then being able to train boxing 2 more days.
I highly doubt their would be too many pro boxers that strength train more than they train boxing. In fact the majority probably dont do a strength training program as such but focus more on boxing and conditioning.