Thinking outside the box, what about the mercedes OM606 turbodiesel? Great mileage and very tuneable. They can be retrofit with a mechanical injection pump from the (i think) OM603. Its a car based engine so it would have more flexibility in RPM range than a 4bt as well as being much lighter.
-Jon
70 challenger convertible. 340/5 speed. blown, intercooled, efi, blah blah blah
71 valiant scamp 318/A833OD/AC/PS
00 dakota RC 4.7L 5 spd autoX'r. SRT10/T56 swap in process
73 W200 Power wagon, PTO winch, 4 spd
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