Dude, RB26DETT is a north / south engine. There's no way u would be able to fit it in a evo5. The evo motor is mounted east/west
Rb26 fit well in a silvia or a 240sx. But it will go much better if you change the sump and gearbox so its only a rwd. Rb25det gearboxs aren't hard to come by.
You need to do the engine mounts. pipe work etc etc. A very expensive conversion.
It used to be a popular conversion a few years ago here for people who have r32 Gtst (rb20det). But its cheaper just to buy a r32 gtr. So there's no point
And with the extra weight in the front of the 240sx. You lose a lot of in corner handling.