Look at the chart in post #35 an now in post #60.. It specifically states stock '77 360 log manifold (probably 1 5/8")....that is nothing near the 360 magnum JGC manifold and it's certainly not anything like the ones I used to machine out to larger than the stock 2 1/4"!!! A stock 76 log 360 manifold would choke a "modified" motor down.