new to me 68 Barracuda Conv, sluggish 318

Here is your cam specs. PAW considered it a "Range2" cam. 16-18 in/hg is what you should get from it.

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Man looking at those catalog images brought back some high school memories....

The issue with 340 heads is not cranking compression is the static compression ratio. On later 318's (not sure what year) it yields a really low compression ratio.

As stated buy a good timing gun and a vacuum gauge. Do some reading here and ask questions. You'll be surprised how easy these are to work on.