Last FT 440 was around 2013, I used Chevron Delo400 SAE 30, with a pint of CD2 street legal oil boost additive.

The CD2 additive is no longer readily available but has good numbers in analysis. I bought a bunch of it on closeout.
Zinc: 4898 ppm (4700) Phosphorus: 4921 ppm (4300) Calcium: 4279 ppm (7800) Moly: 0 ppm (0) Vis @100C: 29.5 cSt (28)