closed chamber 714 casting 318 heads

You will be bumping the Scr up from about 8.36 to 9.35sealevel.
And the Dcr from about 7.7 to 8.61.......(assumes an intake closing angle of 40*atdc)
8.6 is on the edge for full-load/WOT with iron and 87. It should work just fine every where else. You may have to delay max timing a bit, but not reduce it. Time will tell. I would do it.
If it does knock at PT, that cant be cured with slightly delayed advance,or a higher octane fuel,then retarding the cam a few degrees might help, but a swap to a one-size-bigger cam might be the answer.
The higher compression is very desireable for fuel-efficient cruising, with the smaller cam. I would try everything possible to make it work without changing the cam.Even if that means installing a dash-mounted, dial-back, timing device.