Hey Mate,
We discussed this a year or so ago and it was decided against because of how much cross-model info there is. Ie, the rb26 is virtually identical across the R32/3/4 and theres not much overall difference between the RB25's and the RB20's have not changed much etc... then the non-engine specific info is all quite similar too.
If you look in the tutorials section, theres a sticky of threads for each model.. We just need to promote that sticky a bit more and point people to the threads.
Hope that helps,
Christian