The ruling Socialists have long sought to exhume Franco's remains and turn the Valley of the Fallen complex near the capital Madrid into a memorial to the 500,000 people who were killed during the 1936-39 civil war he unleashed.
A crane will lift the slab and, if the original zinc-lined wood coffin is too degraded, the dictator's remains will be transferred into a new coffin, the sources said.
Twenty-two of Franco's descendants will be present for the exhumation, which is set to start at 1030 (0830 GMT) on Thursday, the sources said.
Some of these family members will carry the coffin on their shoulders to an awaiting helicopter - or in the case of bad weather, hearse - which will take it to the Mingorrubio El Pardo cemetery north of Madrid, where Franco will be buried alongside his wife.
A short blessing will take place within the Valley of the Fallen and a full Mass will be held when Franco's remains arrive at the cemetery.
If everything runs according to plan, the whole process should take one hour. The entire operation will cost the Spanish government up to 63,000 euros ($70,000).
The family disputed the exhumation in courts but the Supreme Court rejected their appeal last month.
The funeral home tasked with moving Franco's remains has not been named for its own safety, the sources said, adding that some of the companies involved in the operation had received death threats.
The Valley of the Fallen mausoleum holds the bodies of 34,000 Spaniards who died during the war, including many from the losing Republican side whose bodies were moved there during Franco's rule without the permission of their families.
Neither media nor the public will be allowed to watch the proceedings, in preparation of which the government shut the Valley of the Fallen, which is due to reopen on Oct. 29.
The location of Franco's tomb continues to fracture Spanish opinion with 43% in favor of the move and 32.5% against, according to a poll published by El Mundo earlier this month.Spain is facing its fourth election in four years in November and moving Franco's remains from the state mausoleum had long been a Socialist pledge.