Other than the highest initial cost, what are some of the long term drawbacks of DD the 97 80-series with the swapped 1HDFTE?
Not many if you're prepared to live with the quirks of an older car.
Noise is one.
Diesel on your hands is another
Sore cheeks from grinning like an idiot.
The HD FTE will be noisier than a modern gas engine.
They are powerful and economical, especially with turbo, exhaust, intercooler etc upgraded.
That engine was never installed in an 80 from the factory, but they're well tested in 100 and 7x series for nearly 20years