Hi, I have a 1986 El Camino that i thought had the original 305 but when i ran the #'s it came back as either a 327 or 350, The casting # is 3970010, that is from the back, i heard that there is another casting located at the front but i cant find one, the heads that it has are 3932441, are they worth keeping, i am hoping to get 350hp or so out of this motor, should i keep these heads or use vortecs, also, does anyone know what this motor was rated out of the factory hp wise?