Flywheel Gross is often 16 to 50% higher than SAE net. The 70% figure is where figures were fudged from earlier in the power curve.
Eg. 351 Boss had 330 hp gross at 5400 rpm, but 380 hp gross at 5800 rpm. Ford weren't lying, they were only telling part of the truth! Come 1972, it was 285 hp SAE net. In 1973, the hot 351 HO 4v was rated at 266 hp net for the deTomaso and Mustangs. It's flywheel hp. At the wheels, it was about 225 hp net or so with a manual gearbox.
It varies becasue of air cleaner, exhast, heat, pressure and humidity, fan type, ancilary losses.
On most cars, you loose 26 % for a manual trans and efficient hypoid bevel diff and radial tires well pumped. And auto will loose 33 to 36%, more with similar tires or diff, even more if the torque converter is not locked up or the oil is cool.
In practice, a 125 hp gross 1968 200 would loose about 50% for gross to net hp, (85hp), and another 26% for power (67 hp).
I'd be looking at the gasoline 2.5 HSC engine from the Tempo/Taurus. It's got the sort of torque curve you'd want with weight around that of the 2.3 OHC or 3.8 V6. The 2.5 is very tall, almost as tall as the 250 I6 it was based on, but it has a long stroke and the ohv has better low-end torque than OHC's. It's easier to package than the 90 degree lightweight 3.8 used in 1982 onwards intermediates . The 2.3 HSC is about 285 pounds, the 2.5 about 308 lbs, by my calcs. The 2.3 OHC Lima engine is about 306 pounds, the 3.8 about 310 pounds.
The importMazda/ Toyo Kogyo diesel found in the FWD Tempo/Topaz/Escort may be a better one. Its a 2.0 diesel.
