383 heads with a plug?

Thanks for the responses guys, I was just curious as to what application may have used this. My guess is it's for a temp sending unit when being used in an industrial application (eg fork lift) and that it was the end of the run for 906's in 71 so stuff just got used up, including the single groove "six pack" intake valves. Get the **** of the shelf and in with the new for 72.