I've recently taken-on a project for large format photography and couldn't be more ecstatic!

My initial plan was to shoot the entire project on 8x10, but I've discovered that that certain images will require shutter speeds at/or around 1/250 - 1/400, and concluded that I might have to fallback to medium format to get the job done - the project itself covers a province that is renown for its wind and heavy seas, which in turn, will require capturing in the work portfolio.

Having said that, and as the initial terms were set on large format, I was wondering if I might gain shutter speeds on a 4x5 system w/Nikkor 90mm f/4.5 and 800 film?

For the record, I don't need any movements whatsoever, and could ultimate resort to using a 6x12 back on a 4x5 system if that would help.
Though other than that, I would love to consider some ideas on how I might achieve the intended results without compromising on the initial terms?

Thanks in advance for all your help with this