The Excel is on an old school, body on frame, 1 ton, cutaway Ford chassis. I almost all ways is it is a box truck like any other. Handling high weight requires stiff springs, matching the springs shock damping rates, and high pressure tires with strong sidewalls. All that stuff makes a truck ride like a truck.
If there were room to do it you can reduce spring rate harshness by using longer, softer springs and shocks, but there isn't room and that can also induce the horrible porpoising that you can get with tail heavy vans.
Different tire brands will ride a bit better or worse for harshness and also handle differently so talk to those that have the Ford Excels and see what they say about that. Getting a ride in other Excels if possible would also give a good comparison before laying out a bunch of cash only to get no improvements.
Later Excels, don't know if yours would or not, came with rear airbags so the pressure in them can change things a lot.
Mostly what we hear on the forum about Excels is that they can be very hard to drive to do wander and wind pushing, with some users even scared to drive them over 50mph or in over moderate winds. A lot of the cures for that are counter to ride quality for the most part. Stiffer springs, airbags in the rear, stiffer shocks, big swaybar in the rear,higher tire pressures. If yours drive well, it may have many or all of those kind of modifications on it.
You can take a look at where the suspension is sitting for height. If the front or rear is getting close to the overtravel bump stops from sagging springs, you will get pitching on bumps or wind gusts sometimes.
Body on frame trucks can also be noisy on bumps, our Chevy is, and that can sometimes trick your brain into thinking the ride is actually rougher than it is. We are all used to quieter, newer, car or lighter truck levels of noise, I think. A couple of us tried putting in earplugs to see if it seemed to also gave the impression of being smoother and it actually did for both of us. Kind of strange to be sure.
You can search the old posts and discussions here and you should be able find the best tire pressures there. 80 in the rear is a given to handle the weight unless you are on larger, non stock size, tires and the fronts in Bs usually seem to like 60-65psi to suit most of our preferences for handling vs comfort. Some like as low as 50psi in the front, but I find the handling of our Chevy deteriorates there quite a bit, but comfort and noise are reduced.
If you do have the wander and pushing issue, the normal first start would be to increase tire pressure in the front to reduce the understeering that causes at part of the issue. There is a lot of, IMO, poor information now that the AI searches find that says reducing front pressure improves traction, but that is only true is you are already way over inflated. The talk about tread patch area, but friction is, in general, not a function of area just materials and total weight on the area. What does change with tire pressure changes is the shape of the patch with it getting shorter front to rear and to a much less degree narrower side to side. Low pressure show a high length to width patch and high pressures give short front length and slightly narrower width.
