it is one of two possible places. could have fallen out and been plugged so it wouldnt be an open hole(most logical) both would be on the passenger side of the engine. one is somewhere below exhaust port 3 or 4 in the block close to the pan(less old engines) verses on the timing cover where its on the passenger side down low on the part that kindof legs out also down close to the pan. (more 60s early 70s style) its just hard to say. might actually not have a hole, iv heard of timing covers that come that have to be drilled out by the buyer. (never have seen this so i dont beleive it) but who knows.
in this video there is a glimps of where it would be located on the timing cover. i relocated it from the back location and drilled my cover out for it. 302 efi to carb swap. retro-fit to 74 - YouTube
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