The proper terminology is a conversion from a "spring-under" or "underslung" spring configuration to a "spring-over", or "overslung" spring configuration... searching for those terms may be more productive.
Many trailers with Dexter axles come with a Dexter publication which may cover these configurations; certainly, the Dexter website does.
In addition to the issues with Victor already identified, and the obvious need to climb higher to get in the door, a higher trailer with the same tires
, springs, etc will certainly be less stable and have inferior handling response. It may be not enough to be a problem, and may not even be noticeable to the owner, but it will happen; there's a reason that cars which handle well are lower.
option is a specific configuration of a rubber-sprung torsion axle, such as Dexter's Torflex; the spring-under/spring-over configuration choice applies only to leaf-spring beam axles, such as in most Bigfoot
trailers, the large (1700 series) Bolers like mine, and very few other moulded fiberglass trailers.