Chevrolet Repair: timing issue after head replacement. 5.7, crankshaft sensor, clock position

Question
1998 tahoe. 4 x 4 5.7 160000 miles

replaced both cylinder heads due to being cracked.  New heads are 100% new.  Set engine at TDC, adjusted pushrods.  Runs fine but idles low.  SES code is camshaft position sensor (camshaft/crankshaft sensor correllation).  Timing mark on balancer is at 12:00 clock position--when using timing light.  Not at mark on engine.  Also, first time pushrods were adjusted it seemed some were loose so i tightend them more.  Thinking this may be my problem I readjusted all of them again per manual...now they clatter really bad.  Is there another way they should be adjusted rather then HAynes way.
Also...when using a timing light where should the mark on balancer be at?

If anymore info needed please ask

thanks

Answer
If you adjusted the pushrods by Haynes instructions, you used the timing mark on the crankshaft, and then adjusted about half the rods.
Then one turn, and adjusted the other half.
That method works just fine...if the cam and crank are properly timed.

Due to several of your comments, I would suggest the possibility that the timing chain timing is incorrect.

Van