Dougs D453 headers with TTI exhaust?

1970 Duster with a 340 4-speed manual steering and brakes. I already purchased a TTI 2.5" full exhaust system for headers. A buddy of mine was going to sell me his TTI headers, but has since changed his mind. So I need to purchase some and would love to save $250. by going with Dougs. Have any of you used this combo and how much modification had to be done?