The VSS information from JTR, http://www.jagsthatrun.com/SpeedSensors_Order.html shows early Pickup TBI ('7747 / ' 8747) is 2K PPM.
I've never tried to use the 4K PPM on a '427 PCM. The 4K PPM might work on the '427, but I don't have any personal experience doing so.
dave w
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