Contact Overdrive Repair Services, they rebuild those overdrive units and would probably tell you what oil to use. www.overdrive-repairs.co.uk , info@overdrive-repairs.co.uk
Check out the International page on https://www.vintagepickuptruck.com , several suppliers listed that have transmission parts , one of them might be able to help.
Try the Dodge page on https://www.vintagepickuptruck.com , several suppliers listed have gauges and they may have some of the parts, glass etc...
That is a great looking truck.
Try The Horn Works, they restore horns but might also have some for sale, www.carhornrestoration.com . Also check the Lincoln page on https://www.vintagepartsource.com , large list of suppliers one of them might be able to help.
Check the AMC page on https://www.vintagepartsource.com. several suppliers listed that have used parts including interior, one of them may be able to help.