Sorry can’t help myself but there’s too much misinformation here. Ill be referring to each trim as 35 or 37, respectively.
1. Preload does not reduce travel.
2. The wheel size does not directly affect travel. I.e putting 35 inch tires on a 37 truck does not increase travel.
3. There are four main differences with the front shocks:
First - 37s have thicker shafts so they can take harder hits. The simple fact is 37s are designed to take harder landing forces than a 35 period. Front shock shafts have been a known weakness. Does that mean 37s can survive higher jumps than a 35 or is it compensating for the shorter available travel to survive the impact? I don’t know I’m not a Ford or Fox engineer but I guarantee someone put a good deal of thought into it.
Second - 37s have slightly increased preload which increases front ride height, stiffens spring response at low/moderate articulation (most likely because the 37 tire can take on some of the ride smoothing work a 35 tire can’t).
Third - 37s have different valving tuning to accommodate a different range of wheel travel as well as better handle harder initial impacts than a 35.
Fourth - Last but not least! 37s have less travel than a 35 because of the taller bump stop design. As has been repeated several times, one inch less travel than a 35 to save the fenders. Being a factory design i am sure there is a margin of error factored on top of that. Can you imagine the embarrassment Ford would have if they sold a stock off road truck than caused fender damage to 5%-10% of the trucks sold? Thousands and thousands of complaints, buy backs, and permanently ruined reputation. An additional margin of error is a small price to pay. I am happy to live with that margin myself and will leave factory design as is.