Both players have recovered from cruciate ligament injuries which kept them out for more than three months.
Last season's top scorer Rudd and club captain Chadwick are both in line to face league leaders Skelmersdale on Saturday - a game that could prove crucial to the Rebels' promotion hopes.
Marginson said: "Stuart got 48 goals for us last year and has been a big miss. Having him back is like a big money signing.
"The lads who came in for him and Dave have been amazing, but one thing we lost with those two was experience.
"A lot of young lads came in and had to learn what this club was all about."
United are 10 points behind Skelmersdale, but have four games in hand on the UniBond First Division North leaders, who slipped to a 1-0 defeat at Giant Axe on Tuesday.
After seeing their last three matches postponed, Marginson says his players are desperate to resume their title challenge.
"It's been frustrating but hopefully they will have that added hunger," he said.
"You can see in training how much they want to get back out there because they know they've got a chance of winning the league.
"One of the bonuses about not playing is the fact that no one has stretched too far clear of us.
"We can go above both Skelmersdale and Curzon Ashton if we win our games in hand. The only team we can't go above is Bradford Park - but we've still got them to play.
"We've been in great form and if we keep on going the way we are, I'm confident we can mount another title challenge."
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Free Red, Manchester (14/02/2008 at 15:28)
Saturday 16th Febuary 3.00pm Skelmersdale United Gigg Lane, Pres cup Monday 18th February 7.45pm Nantwich Weaver Stadium, Water-lode, Nantwich CW5 5BS, Wednesday 20th February 7.45pm Chorley Gigg Lane, Saturday 23rd February 3.00pm Bamber Bridge Irongate Ground, Brownedge Road, Preston, PR5 6UX, Wednesday 27th February 7.45pm Clitheroe Gigg lane, Saturday 1st March 3.00pm Bamber Bridge Gigg lane, Wednesday 5th March 7.45pm Curzon Ashton Gigg lane, Saturday 8th March 3.00pm Bradford Park Avenue Horsfall Stadium, Cemetry Road, Bradford, BD6 2NG, Wednesday 12th March 7.45pm Ossett Albion Queens Terrace, Dimple Wells, Ossett, WF5 8RN, Saturday 15th March Newcastle Blue Star Gigg lane with the small matter of a Mcr Prem Cup semi-final on Wednesday 18th March 7.45pm Radcliffe Borough Stainton Park, Pilkington Road, Radcliffe,M26 3PE.
If we come through that little lot in poll position then I'll start to believe we're on for three in a row. Phil Priestley has been brought back into the first team as cover for Sam Ashton and all our injured first team players are back so it's going to be a rollercoaster from here on in. Viva la revolution, come on FC.