I was at my LHS on Saturday and noticed a 1/25 Chieftan tank, the price seemed very good for a large kit so I picked it up. As I was paying for it the sales man said it was an old Tamiya kit, is this so? Is the kit ok? Can I get PE for it and other accesories?

not sure about P/e but it is the older tamiya kit look out for the t-34 by toystar thats the old tamiya kit as well

it is junk
and not very good junk at that
1 it is a mk2 pre production kit
2 the box artwork is a mk 3/5 production unit
3 there is no turret side bins
4 the searchlight houseing is the older style
5 the gun is the old L7 105mm and not the 120mm
6 the there is no rear long bins
8 the engine deck is the wrong shape as are the grills
9 the forward side bins are cliped and face the wrong way
10 there is a grate lump of plastic covering the front plates
so you now have the makings of a good old fashond cut n shut job
if you need help with this i am on my second one and given time and keep to my medcation my doctor thinks i will get better .have fun
eddie jones

As the other poster mentioned, it is indeed the old Tamiya, and goes to show that even King Tamiya screwed up. All the current 1/25th kits are ex-Tamiya, even the "newish" Academy Panther G and Early/Late JagdPanther have Tamiya genes.
But at that scale, I'd be happy to work on an old Tamiya 1/21st PzIII or StuG!!!