Hello again Jrivers0688,
*
THIS* is what sets the ignition base timing on your Vortec 350:
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(credit: Google search "Location Vortec 5.7 CKP sensor
LINK)
And here's a video where a GMT400 owner goes through setting his CMP Retard to within specs.
It's all in there:
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And after watching that video, if you go back to reply #11 and reread
it, it should all come together for you. You have everything you need
to know in order to to fix your P1345, you just have to piece it all
together.
Let us know what you discover.