Guys, I want to thank you for the responses. What it all boils down to, ya'all have about the same ideas and opinions that I have used for many years - use what the manufacturer would on a new engine (this is a SBF crate motor) and that is Motorcraft oil 5W-20 (I'll be using their 5W-30, I made a mistake in my first post). My intent is to tune the engine and run it a few miles 100 to 300, dump it refill with Motorcraft 10W-30 and run another 200 to 500 miles change again but to Mobil 1 10W-30 or 40 and run that forever.
I've had excellant luck with the Mobil 1 after trying Castrol and Valvoline synthetic oil in my '01 F150SCab w/5.4 and my wife's Escape. With the Castrol, a quart would "disappear" in 1000 miles or so. This happened 3 times in both vehicles. No problem with the Valvoline. I finally read some engineering reviews and Mobil was about equal to Amsoil - Castrol wasn't even in the running. With the Mobil 1 @ 5000 miles it is always down just about a pint. I wont pay the ridiculous price for a Mobil 1 filter though - has to be a Motorcraft or Purolator.
As far as emissions - I really don't care - it's a street rod with a carb, no cat on the exhaust and an a warmer camshaft to make sure the emissions stay high.
Zinc is one of the heavy metal nasties that are purported to to pollute the atmoshere along with lead, mercury, copper, nickel and cadmium and a few others.
A couple of web sites describing the deleterious effects of this crap(reading them might cause brain shutdown and a put you in a state of suspended animation called "sleep":LOL: ) :
http://www.fairfaxcounty.gov/nvswcd/...heavymetal.htm
http://drake.marin.k12.ca.us/stuwork...ct%20main.html