Paul Murray, Malcolm Murray, Scott Murdoch and Alex Wilson vowed to restore "trust and transparency" to the board as they called for "sweeping change" at the club's annual general meeting on December 19.
The quartet, who forced a vote on their appointments through court action to postpone the AGM, have offered their services for free and published a constitution making several promises to fans.
Among these are that Ibrox Stadium can never be sold; there should be fan representation on the board; directors and close associates should have no interest in any club contracts; and executive remuneration should be properly controlled and independently benchmarked.
In their letter to shareholders, the group, who each need 51 per cent backing from shareholders to secure their place, say: "The very future of your club is now at risk. The finance director (Brian Stockbridge) told the fans there would be only £1million left by April.
"We have had conversations that give us absolute confidence that new private and public investment will be available on the basis of significant board change."
The letter added: "There are not many businesses who can choose to ignore their customers. This is what the past and current board have done and are still doing.
"All shareholders should be worried about the impact this may have on future season ticket sales and other commercial revenues."
Paul Murray was a director of oldco Rangers before being removed by Craig Whyte after opposing his takeover in May 2011. Malcolm Murray was chairman of Rangers but was voted off the board in July, while Murdoch has his own retail property advisory business and Wilson is a human resources director who has worked for the likes of Ford, Diageo and BT.
Their letter claimed that Murdoch and Wilson were approved by Rangers' then nominated advisors Cenkos at the time of the club's share issue last year.
"We do not believe that there are any regulatory impediments to any of us joining the board if elected," they said.
The current PLC board features Stockbridge, Greenock-based businessman James Easdale and three recent appointments - chairman David Somers, Norman Crighton and chief executive Graham Wallace.
The four prospective directors face a battle to be elected as Easdale's brother, Sandy, controls more than 23 per cent of shares while the club's largest shareholder, Laxey Partners, has stated it will support the current board with its 11 per cent stake.
The main Rangers fans' groups have thrown their weight behind the four men's bid to join the board following a series of meetings.
A statement on behalf of the Rangers Supporters Trust, the Rangers Assembly and the Rangers Supporters Association read: "Our concerns as to the regulatory, fiscal and moral governance of the club have not been satisfied by the board representatives.
"In contrast, the other group have entered into sensible and constructive ongoing dialogue with us and have confirmed some critical matches in their vision to ours."
The statement added: "It is evident that significant portions of the support want as a matter of urgency to see a RIFC board working efficiently as a unit to take the club forward effectively both commercially and on the pitch.
"Failure to achieve this will potentially result in fans disengaging with the club and the effect this would have on income streams would be disastrous."