240Z - RB energi, S13 rear-axle housing

[Fluen]

I seek your assistance, point of view and experience about 240z and mounting of rear-axle housing and RB energi.
Currently I am about to put a RB25DE in the car and the rear-axle housing is no longer useful, wherefore I consider to replace it with either S13 or with the original and instead spend money on upgrading the later.
Right now the rear-axle housing is rusting away.

Not only do I look for durability and driveability, but also for easiness on obtaining the spare sparts, e.g. brakes, bush and other wearing parts. Therefore, I am considering the S13, since it is cheap to obtain, easy to get spare parts for and easy to upgrade with LSD and brakes, springs and shock-absorbers.
would like to keep the engine as NA engine and therefore the choice has been automatically at RB25DE. have so read the RB26DET is the best when you want high revs.
is RB26DET cylinder head just to throw onto RB25DE block.
've been looking for info on gearboxes but could not find anything about it. all 5 speed transmissions same leverage.
how will the 6 speed gearbox box on motoreen and 240z

The car is for street use only.

Now that I have brought this up, do you then have anything you think I should take a closer look at, e.g. upgrading of rear-axle housing etc.?
My plan is to shop at Gabriel from T3, since I already use a fair amount of his parts on some of my other cars (AE86, TE37 and TE70

[RB26powered74zcar]

This section of our forum may help  > http://forums.hybridz.org/forum/31-nissan-rb-forum/