Allen, 46, who succeeded Andy Hessenthaler on Thursday when he signed a two-year deal, has appointed John Schofield as coach and James Russell as strength and conditioning coach.
Scally told the club's official website: "It's no secret that I met Martin a few years ago and interviewed him for a role and was hugely impressed then. I was a bit scared of him to be fair but I'm a bit more experienced now and he doesn't scare me anymore!
"Hessy and I sat down and we wanted someone different who could bring something different to the football club that we hadn't previously had. Every time we got down to shortlists Martin's name was on it and the more I talked to him the more comfortable I got and the more sure I am that we have got the right man.
"I don't want someone to come in here who is a traditionalist or just go along with the way it is. I want someone to come in here who is going to do things a bit different and Martin fits that bill.
"He's a man's man. I've already sat and watched him perform in front of the players and it was lovely - it was nice to see, it was refreshing, it was different and both Hess and I both agree it was a good choice."