Next thing to be done was find out a way of remounting the brake booster. My original idea was to remote mount the booster on the passenger side of the engine compartment as I have heaps of room there now since the spare wheel can't live there anymore due to the engine transplant. I was planning on using a booster out of a Hillman Hunter. There was a problem with that though. These boosters have one line in and one line out. Therefore in order to retain the Niva's dual circuit braking system I would have had to fit two boosters in parallel. Also a local brake specialist reckoned that these boosters were notoriously unreliable and that remote boosters were generally speaking a pain in the backside. His advise was to stick with what I had and simply space the booster of the firewall. So spacing the booster of the firewall is what I have done. This was a really easy job. I was able to use a booster spacer out of a Mk2 Ford Escort.
Believe it or not it actually bolts straight onto the firewall using the existing Niva boltholes. All I had to do was cut it down in length and make up a new flange on the end of it to accept the Niva booster. This is what it looks like just after welding it together and when trial fitted to the car.

Note where I had to fit the fluid resevoir. I has to be above the level of the master cylinder of course. A fact which initially escaped me until I had fitted the spacer, which is the reason why it looks like an afterthought, it is!!
A longer pushrod has to be made of course. I made mine out of 12mm round bar with fittings on either end to fit the brake pedal and booster. On the booster side some provision has to be made to ensure the pushrod remains in a straight line with the pushrod going into the booster. I am also thinking of fitting a reinforcing strap from the booster spacer to the chassis or mudguard to stop any sideways movement and flexing in the firewall when standing on the brakes, hopefully resulting in a more positive and harder brake pedal. The only other thing that's left to do is make up two new, longer brake lines.
Now I can concentrate on fitting the rest of the power steering.