And don't forget that these durability dynos do not use "run of the mill" gas station fuel. They run specific certified ($$$) fuel as you cannot afford a failure due to a bad batch of fuel.
And as stated above, if you assume a bsfc of 0.45 (in English units), and the engine makes oh, say 600 hp, you can see youre in that 50 gal/hrs range. HP goes up, fuel consumed goes up.
Lets not forget the thermal cycling tests too...start the engine dead cold, immediately go to WOT and hold at peak power, wait for the coolant to get near boilover, shut off and immediately run cold water through it until the engine is stone cold again. Now repeat for thousands of times. Or how about piston scuff tests or .... I'll stop there.
As much as I (and a bunch of we on this forum) love these old engines, the testing done on today's engines would destroy these old engines in short order.