None of this adds up to me.
The #13 heads would need to be shaved down to about 65-68cc or so to make 10.4 comp on a 350. That would be similar to a '69 350HO with #48 heads. You'd also need thinner head gaskets than the Fel-Pros and either .005 or zero deck height.
If it is actually 10.4 CR, that's well above the safe limit for pump gas, with iron heads. And, if it has cast pistons, that's not good for a high comp pump gas engine.
That cam is way to big for a mild street 350. Plus, it's one of the steep ramp cams which is said to increase cylinder pressure. This will further increase the chance of detonation.
IF you knew all the specs, such as valve relief volume, deck height, head cc, gasket thickness, etc, you could plug the info into the CR calculator and figure the CR.
http://www.wallaceracing.com/cr_test2.php