[PeteatRoedale]

After working on many examples of all the models i'd say stick with whatever you have, Tikka make a robust long lasting accurate rifle. If i was going to buy a Tikka today and was faced with a choice of T3 or an older model, i'd go with the T3 simply due to the availability of aftermarket parts.
The older models can however be made to work with AICS magazines, you just need to machine the action to accept the mags. Fitting a Rem 700 AICS mag system to the older Tikka's is a relatively simple machining task. but far easier is fitting a T3 AICS mag system to a T3. Our RCS chassis can surely be remachined to accept the older models ( but unfortunately ive no older actions here to try it out with) McMillan and a few other companies will machine you a stock for the older actions also..

The T3 is getting popular because of its value for money. and that will see the growth of the after market parts industry follow suit.
rgds Pete