A stock intake with an Edelbrock 1406 wont work right until you remove or block off the EGR plate underneath of it. Also, the 1406 as received needs to be richened up some for a 351W (I assume it's a Windsor)
As far as CR, 93 octane should work just fine - but those valves, unless you have installed hardened seats will 'go away' eventually. Lead substitute will only prolong the inevitable for a while.
These are not a particularly temperature sensitive engine, but 200* should be your limit.
Pistons - a 4bbl engine will probably have flat tops. The 2 bbl will be dished and is an eventual choice.
Vacuum leaks - gotta check the hoses and carb base gaskets.
Timing - 6*?? These are 9-10 normally