we hAve sanderson on the 429 installed per directions. no problems in running engine, but only in garage so far.
I had great experience with sanderson. we needed custom headers on the driver side to accomodate the Toyota steering box (power steering for 51ford truck). contacted sanderson because we had a set already and their site mentioned custom headers. they shipped me q box of tubing, I cut and arranged it and tacked. sent it back, they made a set based on that and sent it for test fit, then coated and finished it. 100 bucks over regular cost.