Wheel Nuts

It has been my experience that only mags need different wheel nuts. I've never gone from splits to steels though either.

Rojas
When I swapped my 75 series troopy from splits to Sunraysia style wheels the original nuts were re used.
Ian

Both the split rims and the alternate steel Sunrasia's for my Troopy have a slight 'countersunk' effect formed on the rim to accommodate the 'coned' wheel nuts. This configuration causes self-centreing of the studs. The same nuts are used on each type.

The softer mag wheels however have a flat face under the nut to prevent 'stretching' of the hole due to a coned nut.

Rojac

I have been regularly swapping between mud/rock tyres on Hilux split rims and street tyres on Nissan Navara steel wheels for the last nine years without any problems. Both sets of tyres are not worn out yet but are too old so three months ago I fitted a new set of ATs on the Navara wheels. They will be the only wheels that I use from now on. They have already been from Sydney to Darwin and back via roads like the Plenty Hwy and many other unsealed roads in western NSW and Qld.

As long as the taper on both wheels is the same they should be ok.

I have just bought 5 steel rims for my Pajero. I also had to buy new wheel nuts to suit as the nuts from the alloy wheels were flat faced and not suitable for the conocal recessed shape of the steel wheels. Depends on your vehicle. Why not check at a tyre retailer?