As accessories you can probably get away with it, as for using them I'm not sure about the wheels being compatible they are a bit different like Stince said.
Ordering proper Pnz IV plastic wheels can be a bit of a pain as most people only stock some version of the metal upgrade wheels. I had to talk to Mato directly to get some and they messed it up the first time, sending me PnzIII wheels first.. sigh ><
This is a good eBay retailer that I've ordered from before, I'm sure if you need a few parts he can get more for you, as he does stock the plastic wheels : http://www.ebay.ca/itm/Heng-Long-Panzer-IV-Road-Wheels-1-16-RC-Tank-/290815104502?pt=UK_ToysGames_RadioControlled_JN&hash=item43b5ee55f6&_uhb=1
I got my tow cables, L48 barrel, bucket and a few other small parts for the PnzIV from him! Best prices for a lot of stuff.
Otherwise [url=welshdragonmodels.co.uk]welshdragonmodels.co.uk[/url] is my favourite part source.
Tiger I - Panzer III - Panzer IV - Chi Nu Kai - Panther G - KV-1b 756(r)
M4A3(76) Sherman - T-34/85 - M3 Grant