Your idle mixture screws are in the throttle body on the front under the float bowl. I have a copy of the service manual for these, they were used from 1979-1987.
If your idle is extremely rich, the power valve may be bad, and I have seen the secondary metering body warp on these and make them overly rich.
Timing should probably be around 10° BTDC with no vacuum connected, reconnecting it should probably put it near 30° BTDC if it is full vacuum like the later ones. 1983 was the first year back for the 460 and most of the specs were holdovers from 1979. I show 2 different emission vacuum diagrams for a 1983. one is pretty straight forward, the other looks more like the later models.
Bill AKA "LOBO"
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"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 2009 Flex Limited with factory tow package
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413