They work with factory heat riser valve. They work with air conditioning and power steering alternator. Stock style exit flange with 3 bolt design with donut for no leak design. They use stock big block run down pipes. Thick, flat flange at cylinder head that will not warp, no leaks.They are designed to fit in tight spaces, same as the stock manifolds. Exit flange is located in same spot as the original but with a much larger design. A short spark plug is needed, this is common for headers. The only modification needed is minor ac brackets and ps brackets. We have test fitted them to a 70 Chevelle with a 350, power steering and ac. The #2 header tube is very close to the steering shaft but clears. Minor modification was needed for AC compressor support bracket and power steering pump needs a spacer.
On our test car car we used Pypes down pipes listed as 1964-77 big block so we could get a true 2 ½ head pipe and they fit great. The item "THORNTON G BODY SBC CUSTOM FIT HEADERS 2 1/2 EXIT FLANGE CHEVY 350" is in sale since Thursday, November 7, 2019. This item is in the category "eBay Motors\Parts & Accessories\Car & Truck Parts\Exhaust\Exhaust Manifolds & Headers". The seller is "dewell92" and is located in Quakertown, Pennsylvania.This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Mexico, New Zealand, Philippines, Singapore, Switzerland, Norway, Saudi arabia, Ukraine, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Brazil, Chile, Colombia, Costa rica, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Antigua and barbuda, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Saint lucia, Turks and caicos islands, Barbados, Bangladesh, Bermuda, Brunei darussalam, Bolivia, Ecuador, Egypt, French guiana, Gibraltar, Guadeloupe, Iceland, Jordan, Cambodia, Cayman islands, Sri lanka, Luxembourg, Martinique, Maldives, Nicaragua, Oman, Peru, Paraguay, Reunion, Viet nam, Uruguay, Russian federation.