Ford used the Y link on twin traction beam and twin I beam front ends. Once you installed a proper track bar, I don't think the Y link steering will gain you any advantage.
If you raised the pitman arm and were able to install a track bar behind the drag link, I think your steering issues and articulation would improve considerably.
Any good parts store will be able to look at those tie rod ends and cross reference the part numbers for the application.
The dual piston calipers were common on F250 and F350's. I would bet Ford used the same caliper on 2wd and 4x4's
They had 2 kinds of caliper retention systems, one was a sliding wedge type pins and the other had a pin with a bolt in it as I recall.
See if you can find a pre 80 F100/150 4x4 in your area. That steering and track bar would work well adapted to your front axle.
I say pre 80 because that was the first year of TTB and Y link steering on a 4x4. F150's had coils and F250's had leaf springs.
The van looks very presentable, I think it would be worth your effort to fix the front end.
Those look like a set of Selctro fee wheeling hubs, under the dial the hubs should have six bolts to hold it to the axle hub flange. If it does then it is the external hub design front axle, which is common to the first year F250 disk braked low pinion front axle which I believe was 1976.
You could be pretty safe to assume that almost all the front axle parts are the same as a 1976 F250 4x4.
I can double check for you but in 1977 when Ford went to the reverse arch front springs like Chevy and the t-case married to the transmission, they MAY have gone to the high pinion front axle. Either way the ball joints, knuckles hubs and brakes were all the same.
A good site to get info on Dana front axles, especially Ford stuff is "Mr N's Dana front axle guide".
Edit: The F250 low pinion disc brake front axle was in use from 1976 to 1977.5. After mid year they went to the high pinion front axle. On his site there are pictures of coil sprung F100/150 front steering and track bars, one photo of a disc braked front axle has a very bent tie rod but it is solid between the knuckles and the drag link goes from the steering over to the passenger side in line with the track bar. An F100/150 type tie rod, drag link and track bar as I mentioned above would be perfect for your setup. If you drop down to pictures of the newer TTB on Mr. N's site you will see a Y steering setup. My guess is you have nothing Chevy on your front end except possibly tie rod ends. The brakes are clearly Ford from looking at the Ford Dana axle pictures. There is lots of info on Mr N's site, stick with the Ford stuff to avoid too much confusion. Hope this helps.