@GLU You need to tell us a little more about the 13" rims. There are 15 different 4 bolt patterns from 3.75" to 190mm. I don't know what they would have in Puerto Rico.
Ranger is 5x4.5" with 70.5mm center bore.
60s 6 cyl Mustangs were 4 x 4.5" with 61.5mm center bore ; never seen 13" but several 14s.
Mustang II is 4 x 4.25" with 63.4 center bore and either 13 or 14s; wife's 4 eye was same pattern with 390 TRX rims.
Imports are all mostly 4 x 100mm
Note: The issue isn't just bolt pattern, you need the center bore to be correct too.
Technically, it is possible to drill rear axle shafts for 4 bolts, but you really would want different hubs for the front e.g. Fox body Mustang if 4 x 4.5" (80s T-bird/Cougars have 4 x 4.25)
There are ribs in back of Ranger hubs which would prevent bolts from seating properly in 4 bolt pattern and you would be damaging hubs integrity if you removed them.