If the OP Has alloy wheels and does not have a steel spare, there is no need to worry about whether the wheel bolts fixing his alloy wheels will work with a steel wheel
Ps, if you do change the alloy wheel for the spare steel wheel, you need to use the adapter plate and the 3 bolt fixing to attach the alloy wheel to the underslung windlass. You also need to place the alloy wheel on a car mat or bit of cardboard etc to protect the outer face of the alloy from being badly scratched by the ground as you slide it under the van to raise and lower it to the storage housing
I would also recommend you have a proper breaker bar and deep socket and loosen & retighten the wheel nuts before you have to in anger. I managed to bend the standard tools that came with the van as one of the nuts was was so tight I couldn't shift it. I only managed as I had access to proper tools
the OP said he was looking at getting a steel spare , hence all the talk about length of wheel nuts
I don’t have a under slung spare wheel , same as nearly all new MH’S (not inc campervans)
I always carry the appropriate tools to change wheels , in fact I carry far to many tools
But thanks for all the advice, kind regards Kenny d