You can’t reliably get the power density of the GTR’s block on alcohol, with a turbo diesel (and I love turbo diesels).
Horsepower is a function of torque and rpm. Directly linear, in fact. To take on the combustion characteristics of a direct injection system, with the amount of torque needed to keep the diesel at a reasonable diesel RPM, would require a block and internal components that would make it impossible to fit into a compact luxury car.
Diesels will continue to improve as material science improves, but I would say for a reliable diesel, the Ford, Cummins, and Duramax diesels are probably at the limit for *reliable* road performance (not dismissing the propane, nitrous, and super-chipped versions of these engines, but they won’t last their warranty period if actually used in the capacity they are tuned too without significant internal upgrades, if run at their peak power for most of their usefukl lives).
Though I haven’t done the math, most of the US is above Sea Level. High Speed Diesels have made great improvements of late. I suspect that a study of the necessary HpHrs nessissary [sic] to get the job done would include a TD.
The objective would be 24 hr. LeMan was won by Ford based on extensive dyno optimazation of a powertrain back in the day.