While the new-for-2017 LMP2 regulations will enforce a limit of four constructors, up to five chassis manufacturers will be certified to compete in the LMP3 category.
The ACO has confirmed the limit in a technical bulletin released last week, which also reveals a minimum weight increase from 900 to 930 kg for and price adjustment for the entry level prototypes.
Currently, the Ginetta is the only LMP3 car fully approved for competition, with the homologations of the Ligier JS P3, Riley-Ave AR-2 and ADESS-03 all ongoing.
The fifth manufacturer has until Aug. 31 to come forward to the ACO, with the final slot appearing to be on a first-come-first-serve basis.
At least two existing prototype manufacturers are understood to be exploring the possibility of becoming the final approved LMP3 constructor.
The cost-capped price of a turn-key LMP3 car, meanwhile, has been increased to 206,000 Euros ($228,000).