With a candy thermometer or a good mechanical gauge I'd find out exactly what your temps are (on the hiway and in town). Take the stat out for 1 day (the slower warmup wont hurt you just for 1 day). check for timing in the ballpark. Have a radiator shop suck up some rad coolant into the bottle and see if the blue fluid turns yellow (indicates a combustion leak) or if you have an emissions testing station close by have them stick the probe into the top of the rad & see if combustion gasses are present (you'll know in seconds). check for a vac leak (not sure the best way to do that). What do your plugs look like. You have a 5 row rad