Found this website, thought it might be helpful.

http://www.rowand.net/shop/tech/SlantSixTBISwap.htm

You can use my Rochester TBI adapter instead. I used a 2-piece design rather Howell's 1-piece design to keep the manufacturing costs lower and to ensure that the adapter's upper plate matches the TBI gaskets.

H'mmm. Are you thinking of blending or bevelling the lower plate's edges so that there's not such a big shelf impeding flow?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Like I said earlier, I went with this design to keep the manufacturing costs lower. The challenge with this adapter is the large difference in venturi diameter and spacing between the BBD intake manifold and the TBI. The upper adapter plate is only 3/8" thick so there isn't a lot of room there for beveling. The lower plate is 1/2" thick, which allows the socket-head cap screws to be installed flush with the top of the plate.

While the flow path isn't ideal, I don't think the "shelf" impedes flow very much because lower adapter's ports match those on the intake manifold and the upper plate's ports match those on the TBI. There is no reason why the buyer could not smooth the ports in the adapter for better flow.