Agreed you don't absolutely need to reset the toe if you don’t change the length of the tie rods. Not a bad idea to check the toe anyway because the front end toe alignment of the old 911 is rather sensitive to ride height and you may end up adjusting the rod lengths anyway if you must reorient the steering wheel a tiny amount.
Here's how I see it and let me know if my understanding is incorrect! Agreed with ClickClickBoom that you start with ensuring the rack is centered by measuring how much rack shaft is sticking out each side of the housing. Rotate the pinion until you have same amount on each side. That'll get you close enough to start. However, your tie rod lengths are going to dictate where the rack positions itself as soon as you install the rack back into the car. But the tie rod lengths won't ensure your steering wheel will be oriented the in the same position it was previously.
Your clocking of the bolting flange on the rack’s pinion shaft is going to dictate the relative position of the T-shaped shaft extension. That T-shaft is going to then determine your steering wheel position by how the T-shaft's splines fit into the U-joint splines. Why this is all relevant is because the T-shaft has a relief cut in its splines
to accept the U-joint pinch bolt. That means the shaft is inserted into the u-joint
only one way. So you'll find that when the u-joint and shaft are connected, your steering wheel is going to be "crooked." This all occurs because rarely does anybody mark the clocking of the bolt flange relative to the rack housing upon disassembly.
An easy way to approach the steering wheel re-positioning is to actually drive the car slowly and safely with the steering wheel nut removed. You obviously want to get the wheels pointed straight ahead before you snug down your steering wheel. So get it driving straight (assuming your alignment is good and the car doesn't pull to one side at higher speeds
) for a short distance, stop, pull the wheel off and reorient it to the nearest spline that puts your steering wheel "straight."
However, even after you get your steering wheel on the desired spline it may not be spot-on at precisely 12 o'clock like you want it to be. If you're OCD and it'll drive you batchit crazy with the wheel off by 1 degree? Well then you would loosen the jam nuts at the tie rod ends and rotate both rods the exact same amount, in opposite directions, to shift the rack position left or right. To shift the rack so your steering wheel will rotate counter-clockwise, you would shorten the passenger side tie rod and lengthen the driver side tie rod. When the rack self-centers, it will reorient the steering wheel slightly counter-clockwise. To shift the rack for clockwise steering wheel rotation, lengthen the passenger side tie rod and shorten the driver side tie rod.
Note that you don’t change the length of the rods by a lot. Like less than a quarter turn if I recall. And you need to be rather precise in your adjustment of the tie rod lengths because any variance in your rotation between them will change the toe amount. That said, you'd have to be way off by a number of rotations to screw it up really bad and have way too much toe in or out.