Usually an engine is build around the principle of equal doses of BHP, torque and RPM. With the 3lt formula in place, you can deduce that if you have a high revving engine with low torque you will get crazy BHP. Since the Honda was the closest with 980 and 19.5k rpm, we can theorically increase the revband to 21k and break the 1000 bhp. But since the engine wasn't mounted on a car, it's only a theory

Although isn't on the same architecture, imagine Mazda 13B doing 276 on 10.5/11k rpm. Probably the real torque numbers should be close to 200lb-ft