400 into 65 valiant

I was looking on my phone for the pictures but I did mock up a couple years ago. If you search the forums on early a big blocks there’s stuff around on them.
The ‘67 was designed to allow a big block. The early a never was. So with torsions bars and full inner fenders it’s tight. Plus the floor and trans crossmember are not designed for dual exhaust. So if you want bigger pipes you will need to address that too, or leave the right side pipe lower.