Factory 68-71 340 puts 325HP on GM Dyno

I just heard from an old guy who lives near here that GM engineers got their hands on a factory 340 in 68 and put it on the dyno and it yielded 325 horsepower but was advertised at 275 horsepower for insurance reasons. He said that the engineers were stunned that an engine that was in the form of the 273 with 235 horse the previous year had jumped nearly 100 horsepower with only one year of refinements. Do you think there is any truth to this? Has anyone here actually seen an early factory 340 on the dyno using the methods from that era to dyno the engine???????