Wheel size change

[Kappy]

Hi
Not sure if this fits here.
I have a 1992 Mercedes OH1418 Ex school bus converted motorhome.
Currently its running 20 inch tubed split rims.
The tyres are getting a bit old and due for replacement, so thought I go for 22.5 tubeless rims and tyres.
With getting into any particular brand, my question relates to the actual stud pattern.
I believe they are 10 x 355 pattern????
Sadly I'm about 1500km from the bus ATM. so unable to clarify.
Inquiries have led me to believe that Mercs can have different wheel nut aspects.
Anyone have any clues on the subject and what may be the correct rim in 22.5 inch for my rig.
Had considered Alloy but believe that's another can of worms.
TIA
Kappy