The .961 will pretty much fit IIRC, the .960 will need parts from the .971 to make it fit.

The ..96x will probably have an older head, newer is better, I'd keep the newer (probably the .971) head and the .971 turbo is trimmed for more boost.

The .971 IP is not designed for the hp (and thus fuel flow) nor the RPM of the .96x, so the .96x IP is IMO better.

Just a matter of "cherry picking" to make an engine that is the best of both. I'm in the middle of taking two good running engines, a 603.960 and a 603.971 and making one very good 3.0. It doesn't have a home yet, but if it's finished before something catastrophic happens to the '87 or I find a 140 diesel that needs an engine, it'll be my super-turbo '87 300D engine. Might as well optimize the "gene pool" of the engine you're building.

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Gone to the dark side

- Jeff