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You won't be sorry with the Langdon headers. They keep the eng compartment cooler, are quieter, and don't have the ambient noise that tube headers have. Being cast, they're also less susceptible to leaking from heat cycles. I put mine on, retorqued them after a couple of heat cycles, and haven't touched them in three years.
Looking at your picture, I'm guessing you have the same problem I had in that your intake flange is about a heavy 1/16 inch thicker than the exhaust header. I ended up grinding the oval "washer" the amount that the intake was proud so that there was even pressure on the flanges particularly since your Offy is aluminum, and you don't want to over-torque the fastener to insure the header is tight enough.