Going with a 16 or 17 would be great, IF they would clear the drum brakes on the rear of the old duallie trucks. The older 1 ton trucks used larger drums that the later disk brake trucks do on the rear, 14" vs 13". On a single wheel aplication, you can get away with putting 16s on the rear (been there, done that), but a duallie wheel sits much further inboard. While I suppose a 17" duallie wheel might fit, a 19.5 will fit for sure. As far as tire size, 225/70/19.5 is only about 2" taller than the 8.00-17.5 that's oem for a '58 3800 duallie. The sidewall hights are less that 1/2" in difference, not engough to be noticable. Yes, the ride quality will suffer, more due to the heavier load range than sidewall hight. Handling may improve some due to the stiffer sidewall.
BTW, 19.5 were a factory option in single and dual on the 3600.
