A Metal Tank Hull is a very good starting point and I would suggest you go to FORGEBEAR's site on E-BAY and scroll through the pages of updates and eventually you will get to a "TAIGEN TIGER 1 METAL HULL" this will come with suspension and gearboxes and a quick release HULL/BODY SYSTEM, The Heng Long body is an instant fit which needs no alterations to mount on the TAIGEN Hull.
But still a lot to do once you get it,
Your first purchase after the HULL should be Metal Wheels and idler's and Sprockets and axles.
You will need to make a decision before that as to whether you are building an early , mid , or late as the wheels and sprockets are different,
Metal tracks look great but are expensive and if you intend to drive your tank over all kinds of terrain then Plastic/Nylon tracks might be a better choice,
Everything I have listed is also available at
http://www.welshdragonmodels.com, Steve being a Specialist dealer in all matters TAIGEN and he has a wide range of TAIGEN Gearboxes including 3/1 4/1 and 5/1 (the higher the number the lower and more realistic the speed)
There are many differences between the different Tigers,
The Early has a completely different Cupola from the Late the exhaust and air filters are also different indeed a good read of these pages will help you much more than I am doing,
But there are some mods that you can carry out free such as removing the redundant Aeriel holder on the rear right hand side (LOOKING FROM THE FRONT) and if you are going to build an early Tiger then the CUPOLA is wrongly positioned,
The TIPS and TRICKS site will tell you how to fix it as well as a lot of other helpful hints

shaun