[jsveb]

If all the controls are removed, this will obviously require some work.

On the headers, some of the options could be:

1. SSIs ( as you mention) this, I believe, will require a socalled Y-pipe to be able to mount the turbo to the headers. RarlyL8 sells this. Also, I think it requires different cross-over oil lines to be able to use SSIs.
I believe the SSIs are at their limit size wise when mounted to a modded 3.3 turbo, but others can chime in on that.

2. Buy a set of rarlyL8 headers assuming you can get them with heat.

3. Buy a set of B&B or equivalent. I think TurboKraft sells those.

It is not terrible difficult to put the heater controls back in. Especially if we are only talking about the manual part. I have just done that, on my Carrera 3.0

If this is a cheap car, and that is what attracts you, but it does require some work. I would skip it and buy what you really want.
It is always gonna cost you A LOT more than you expect.

Good luck