Complety false, I have never seen a dodge with an 5.5" pattern.
I have had the following tucks and they all had the 4.5" pattern with 8.75
56 dodge
69 dodge
71 dodge
The 56 Dodge had a Chrysler 9-5/8" Axle in it (the axle the 8.75" was based on in design) if it was the original rear. Those are 5 on 4.5" (dating back to the 1930's)
All 4WD 1/2 Ton Dodges 1974 and earlier (I forget when, sometime in the early 60's) are 5 on 5.5" pattern. Apparently the 2WD's were 5 on 4.5" (I had to look that up, not much of a 2WD guy. That's where I goofed up). 8.75"s were more common in the W100 (4WD) than they were in the D100 (2WD). You're more likely to find an 8.25" or 9.25" under a 2WD (but 8.75's were an option).
So keep that in mind when you pull a rear from a truck, the 4WD's ARE 5 on 5.5" up until 1974 (and in 1980 they went back to 5 on 5.5" on the 4WD's again) The change from 5 on 5.5" to 4.5" involved the changeover to the NP203 Full Time 4WD Transfer Case and its Unit Bearing Hubs with Drive Flanges (No Hubs/Lockouts). When they went back to Part Time 4WD in 1980, they reverted back to the 5 on 5.5" Pattern for the 4x4's again.