On a sunny day with ISO 200 film / setting and aperture at f/16, set shutter speed to 1/200 or 1/250.
Personally, I'm a big believer in ISO 100 films when I'm shooting color prints on a casual basis.
Let's say your flash has a GN of 80 with ISO 100 film, and your subject is 10 feet away.
For example, a photographer may rate an ISO 400 film at EI 800 and then use push processing to obtain printable negatives in low-light conditions.
For example, the Ilford product is actually an ISO 1000 film, according to its data sheet.
It also works well in moderate depths under water when there is adequate light and it is preloaded with fast ISO 800 film.
For a 2:1 ratio of daylight to flash, you'd double the film's speed, rating a ISO 100 film at an index of 200, for example.
When you use a 400 ISO film with the lens in wide-angle position, the flash covers from 2 feet to 27.6 feet.
With ISO 400 film / setting and aperture at f/11, set shutter speed to 1/400 or 1/500.
And should slower color films be pushed, or should Kodachrome 200 ISO film be used instead?