Thanks for the comment Lionel,
"what made me doing that"? maybe i took leave of one`s senses!?! Due to i broke a gearbox by launching another pulsar of mine the thought was born. I was looking to adopting a gearbox from another, more reliable car. I found threads where guys flanged audi gearbox onto the SR20, others did it with celica gearboxes from toyota. So i thought, why not sticking to nissan?
There was no reliable nissan box to be found in lateral mount. But the Skyline box and the whole attesa system atracted me. So the thought was born placeing it lenghtways. Due to the fact that i had to change the gearbox tunnel and the bulkhead for the skyline gearbox anyway, the thought that the RB engine might find enough space was the next. So is how the story of all that started.
I`ve not measured the weight of the RB26 setup yet but from researches in the web i´ve found out, that the difference is around 150kg. Almost all the weight of the sr20 and the gearbox is beforehand the front axle. The RB setup balances over the hydraulic support (image below), so the weight is therefore brought more to the back of the car. This should balance the additional weight throughout the car.
Also there are alot of parts to support the engine, gearbox and to rainforce the cutout, this brought some more weight aditionally. I expect at least 200kg more than with the SR setup.