http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXJFE2 This is the tank I use, drops right in, just have to move the rear tank mount back, there are already holes in the chassis for this.
As far as break in, the alternative to following the manual is look on page 121. 46u posted a different way to break in the motor and I am somewhat following this method right now except for the first tank part. For that I am combining hpi's method of letting it idle and varying the throttle (while on a stand, tires off the ground) to keep clearing out the excess fuel. And in case you don't know (when reading 46u's post) to find bdc, rotate the flywheel until it is easy to turn. This is bdc, if it is hard to turn, you are either entering or leaving tdc.

Also, if you use this tank, you may want to add an extra o-ring under it on each screw where the screws go through to bring the height up a little so it doesn't rub the chassis. Although with the stock tank on mine, it also rubbed a little, but this tank seems to be a little deeper.