oldejack wrote:
looks pretty good to me. i agree with adding the 3 green bars, the weight of the rearmost ones aren't much and since most of the box beam making up the frame is gone you may need the bracing. in addition the lower front link attachment points (rear suspension) may need strengthening for the same reason. ...
I have to agree with everything Jack said and I'd like to suggest going a bit further. I'm an Evo guy and I know the kind of violence that a 4G63 is more than willing to transmit to the rest of the car once it's pushing some decent power.
First I'd suggest including all the subframe and/or suspension pick-ups in your triangulated structure. Think carefully about where the loads from your driveline will be passed into the chassis through the suspension pick-up and sub frames and then make sure those areas are well supported.
Be sure to tie in the engine and transmission mounts from the unibody as solidly as possible; you removed almost all of the structure that used to support those areas of the chassis so adding back structure will be important. You may even want to look at providing some support across the front of what remains of the chassis to help keep the engine bay from deforming when the engine/driveline loads start to move everything around.
I would even recommend adding back the front engine mount and the cross member that goes under the engine bay from front to back; I once had my Evo tear the back ear/mount off the transmission case (housing) because it was spinning then hooked up traction and delivered a very expensive, part-breaking shock to the driveline. Even with all the OE mounts in good condition and fully in place .. but I was on very sticky rubber.
Very cool project