I have the 6 lug bud wheels on a M105 with 9.00x20's and also have some Hummer wheels/tires that have 8 x 6.5". I designed a 1" thick plate with proper drilling so the 6 bolts can be reversed and the nut used on the trailer hub. With a countersunk hole, the top is flush. New studs then protrude the other way for holding the wheel. It's not that complicated for a machine shop to do countersunk holes (on reversed sides of the plate) on the two different bolt circles. There is no bolt interference if spaced properly. I laid it out full scale.
As I have a new trailer axle with electric brakes I'm not going the adapter route but instead using the bed on a fabricated frame with my wider, lower Hummer wheel/tires. Thus I'm doing what Recovry4x4 suggested after making a drawing of the adapter. The reason for me, at least, is because I get two trailers from the one, using parts I have already. But the adapter route is entirely possible for getting one lower and wider.