You say the bridge is 40" long. Approximately how many pounds does it weigh?
Don't mean to insult anyone but basic high-school physics will ballpark the maximum (worst case) pounds the linear actuator must deliver to raise the bridge (starting from horizontal). Since travel of the linear actuator is less than 1 foot, you would presumably couple the linear-actuator a relatively small distance (also less than 1 foot) from the pivot point.
I'd think 200 lbs is more than adequate (no counter-weights needed) but why not measure-twice, cut-once. Doing the math might also suggest you only need, say, a 6" rather than 10" travel though it doesn't seem there is a gross cost penalty to buy the longer versions.
