Classic/Antique Car Repair: smokey exhaust, valve seals, wt oil

Question
I currently own a 1971 Ford Falcon australian made muscle car with a 302 v8 in it, and recently replaced the heads due to suspected cracked heads. Although the heads have been replaced along with all gaskets etc. there still seems to be a greyish smoke coming out of the exhaust. There doesnt seem to be too much smoke when starting it up, but if left to idle, or reved a little, the smoke seems to thicken up a fair amount. I was told that this may be due to the engines age and therefore being full of crap. Could this be the problem, or could i have a bigger problem?

Answer
HI JOE;
       Sorry , I thought that I sent it out but it did not go so I was told by the staff to re send it so here goes  ok.
The valve seals might have been bad or old and causing the smoke , but due to the age of the engine I think it is time for a over haul , but first did you do a comp. check on all cylds.  if good the valve seals could be bad as oil burns white thick smoke that does not go away fast, gray smoke could be the fuel mix in the cylds. with some oil from the valve seals, you can try a HOTTER spark plug  go up to the next or second higher plug and see if that helps you. but I would change the oil and filter and put in a straight 30 wt. oil. As far as the valve seals , there is ways to replace them ON the engine in the car. with the right tools.