Hi,
I put mine on the collector, just upstream of the reduce flange. I welded it about 2 o'clock if looking from the rear, forward. It does not hit anything. I have a Autometer Wide Band Sport Comp A/F Meter. It uses a Bosch sensor. It came with a bung to weld on the header. I also have a Sport Comp vacuum gauge next to it. I get vacuum from the old PVC port on the TR-4a intake. Watching the two at the same time tells a lot.
Shop Summit, Jegs, Speedway, etc for a sale.
Roy