THE SHORT ANSWEROnly When Installing WA-0492 on pre-2002 G-ClassThe main consideration for whether these Hutchinson wheels "need" spacers to go with them is: Which type of Hutchinson wheel do you plan on matching with which year of G-Class? In brief, though, the only wheel for which we believe you "need" spacers is the WA-0492 when trying to install on G-Class trucks manufactured before 2002. The reason is because Hutchinson staff received reports from customers that the wheels hit the tie rod end at the front passenger corner of the truck.
OTHER CONSIDERATIONSAestheticsAnother consideration for whether these wheels "need" spacers is aesthetics. If you like the look of having your wheels shifted out, get them. Our feeling is that the WA-0492 wheels look a little "pushed" inward when not installed with spacers. Not so much the case with the WA-1873s. We believe that spacers that are much thicker than the
31mm H&R spacers we sell would create too much leverage, so we don't usually go beyond that.
RubbingYou mentioned mud tires. If those are extra thick and beefy, whether they create a rubbing issue in the wheel well may depend on the actual tire size. Different tire manufacturers sometimes measure the tire differently. This can result in tires that are actually a different size being labeled the same size. Whether your mud tires need spacers because of rubbing depends on the actual size of the tire. But having your tire sit further outward may not always resolve a rubbing issue. If you push it too far out, it can create rubbing in a different spot. The "calculus" of whether to get spacers to eliminate the rubbing created by larger tires gets tricky.
Here's more info about the wheels and the fitment information that Hutchinson has shared with us.
WA-0492 (FLAT-FACED MILITARY STYLE) - Spec Sheet Attached

Hutchinson indicates that these are made for G-Class trucks from 2002 to present. Please know, however, that as of the date of this writing (07/24/2020), we have not sold or tested any Hutchinsons (this model wheel or any others) for the newer G-Class (W463a - the 2018 and newer models), so Viking cannot vouch for fitment of this wheel or any of the other Hutchinsons on the newer vehicles.
Re. fitment on vehicles manufactured before 2001, Hutchinson indicates that this wheel will hit the tie rod at the front passenger side corner. This is the situation in which spacers of at least 15mm thickness are strongly recommend. It's best to get the spacers for all four wheels.
WA-1873 (HUTCHINSON WITH CONCAVE WHEEL FACE) - Spec Sheet Attached

This one is made to fit trucks from the 80s and 90s. According to Hutchinson, it also fits G-Wagens of years all the way to the present. We haven't verified.
WA-2059 (18-INCH HUTCHINSONS) - Spec Sheet Attached

We haven't fitted these on any wheels as of the date of this writing (07/24/2020). However, Hutchinson indicates that these are made to fit from 1990 to present.
In the attached spec sheets, note the offset of each respective wheel. WA-0492 & WA-2059 have the larger offset number at 63mm vs. 37mm for the WA-1873. This larger offset has the effect of making those wheels look like they sit inward on the wheel well in comparison to the WA-1873. The mounting point of the wheel sits 63mm beyond the center point of the wheel, "pushed" toward the outer rim. In order for these wheels to mount, the wheel must sit further inward than a wheel that has a mounting point with only a 37mm offset.