I just power washed a 383 in the GTX I found setting for 20 years.Not the original 440 so already disappointed. Take it on a test drive, open the hood to find puddles of oil on the front of the block below the intake. Is this a bad gasket some where?

 

sounds like it, intake or valve cover

 

Or the valley pan could be cracked..

 

I would say either valley pan and/or valve cover gaskets. Both are very easy to replace and are cheap enough. I would do both and call it a day.

 

I had the same issue. The intake/valley pan was cracked under the intake where it could not be seen.
You may want to get a gasket that blocks off the heat cross-over. Use silicone on the front and rear.