quick question
 

Would 255 50 19 tires fit to my pacifica?

2cm difference in width of a tire won't be a problem I guess.

Factory tire is 235 55 19 and it makes pacifica look more like a minivan than a crossover.

Should fit with no issues as there's only .200 difference in the diameter. (stock=29.2 and new = 29.0)

Here's a tire size calculator site.
http://www.miata.net/garage/tirecalc.html