Boeing (in olden days) has always countenanced using all the R/T available - to the extent that GE had to put a R/T Limiter device (to prevent overboost) on the CF6-50E for 747-200/-300's.
But aren't -200's (JT8D) still managed to EPR, not N1? If R/T ops state an N1 figure, doesn't that imply the CFM56?