As this was a cold-war military device, details are not completely known. It seems to be officially unclassified as of 1980 though it possibly never was classified. (US military sometimes "unclassifies" documents that were not actually classified to start with. Such is the nature of bureaucracy). I actually rode one of these when I was was a kid and even got to fly it for a minute or so. I was merely warned not to bring a camera or audio recording device but I think this was more to do with other tech at the base, or the base itself, rather than a flight simulator that was slightly older than I was. The operating manual could be purchased by the general public in 1974 for $0.75 plus $1.85 for shipping and handling. "Approved for public release; distribution unlimited." But it was merely an operating manual, very light on technical details. It is all about training pilots and minor system maintenance, certainly not for system repair. Components are described as what they do or are ("CPU", "MEMORY MODULE", "SPECIAL PURPOSE COMPUTER", "GENERAL PURPOSE COMPUTER") rather than being identifiable names along the lines of "Intel 8080" or "Zilog Z86295". However, it does specify "System Engineering Laboratory (SEL) 7200 computer". I've yet to find any info on this computer. The fact that it could interface with a SEL 8600 plotter suggests that this 7200 may have been a version of one of SEL's 8000 series computers. The manual also refers to 2 SEL System 86 computers (There is a SEL 8600 computer).
The manual mentions Assembler, FORTRAN IV compiler, and BASIC compiler which is consistent with SEL 8000 series computers (but other computers as well).
Note, it is also entirely plausible that the 'SEL 7200' and 'System 86' are intentional misinformation.
Update: System 86 does exist
source: assembler, FORTRAN IV compiler, a BASIC