As you can see the rails are welded in. See how I don't do a solid weld end to end. Not needed, and the extra heat would warp the chassis.
Now this is inside the side frame panels. I use the same tubing to stiffen the box or tunnel of the frame. Makes for a solid chassis and it isn't add much extra weight either.
Ok here you see where the E.C. Distributing tranny plate buts right up against the front sub frame. ALSO it goes in the tunnel and sets on top of the frame rail supports. You can bolt or weld it in I choose to weld it then it becomes a part of the frame and helps stiffen it.
Here you see that I have mounted a tranny lower case. Then you slip the plate bushing into the the hole which self aligns on the input shaft.
As you can see it aligns perfectly. Now tack it in place and then remove the tranny case wnd weld it completely in.
Here it is welded completely in place. This bushing supports the weakest link (the input shaft) of the 700 tranny and with this setup if you break the input shaft it is due to case fatigue or worn or bad bearings.