WSMMAD is correct. You can order the 30-06 mag from tikkaprecision.com (they usually have them in stock but are slow to communicate) for around $70. BerettaUSA has them in stock off and on as well.
I have modified the magazines on all of my Tikkas to accept VLDs.
One note on moving the bolt stop back: Take your time! Depending on the year of your Tikka, there may be a delineation line to go off of or there may not. My T3 from 5 years ago did not but the one I bought last year does. I measured the necessary clearance probably 6 times, took the bolt release off the gun, and slowly filed it back checking for fit numerous times.
The easy (read: expensive) way is to order a replacement bolt release assembly from Brownells. It will come with both the long throw and short throw stops in one package. All you would need to do then is drop in the long throw with the 30-06 mag.
The fun way is to order new bottom metal from CDI Precision! It accepts AICS mags and the machining is superb.
I am currently building and F(TR) on a T3 action. Jeff at the CDI spent quite a bit of time answering all of my questions and is an all around great guy. I now have the metal sitting on my workbench while I wait for Manners to complete my T4-A
Tikkas are excellent guns to own if you have the patience to hunt down the minimal aftermarket for the gun. The good news is that the few companies making aftermarket parts for the Tikka are all very reputable and provide great products and support.