Idler Arm hitting header.
I've also had some success loosening the motor to mount bolts ( 3 ea side),, and jacking the engine up, and re-tightening the bolts, or combo jack/moving the engine around with a bar, and retightening..
Loosening the header flange and lifting the collector may gain some clearance as well.
Shimming is an option on the biscuit mounts,,
I;ve also had sucess using a ratchet strap around something secure, (trans, or torsion bar) and slightly bending header as nec..
Denting the header should be a last resort..
cheers