I'm trying to assess the conditon of the 302 in our mav. The low down:

-milage 89K (original), all stock equipt (incl. 2 barrel car, CA smog equipt.)
-cylinders 7 & 8 seems to get the plugs fouled with excessive carbon build up and oil. Intermittently plug 5 has also given the same result, but not recently.
-Compresion test shows approx 140 compression across the board (dry, didn't have a chance to do wet test)
-The engine idles pretty smooth and there is plenty of power
-Oil is blackened farily quickly (doesn't this mean excessive blow by?, or just crud in the oil pan)

So my qustion is what should i do to asses the engine's condition so I can figure out what my next step should be. I'm thinking that the valve seals and or guides need work, but I'm wondering if it would be better to go ahead and pull the heads and have them rebuilt with hardened seats, etc. And before i get myself deeper into this what should i do to determine the condition of the bottom end before rebuilding the top end?

Well thanks everyone,