basicaly its just the normal Panzer IV with an Eduard Zimmerat set
so looking on a UK web site the normal
Pz IV J with the zim kit your talking about is £39.99
Pz IV J is £25.99
Pz IV H is £23.99 (i dont know why its cheaper than the J, its basicaly the same kit)
the Eduard Zimmerat set for the Panzer IV is £9.25
so you could get them both for £35.24 for the J
or £33.24 for the Panzer IV ausf H (basicaly the H is the better one becouse its got the Shulzen with it )
so i think the Tamiya kit with both is a bit of a Rip off when you could get them both Separately for alot cheaper and most Panzer IV Js didnt have Zimmerat
if you look in the Panther group build some in there are using the Panther Zimmerat kits