Building a reliable motor

[crm318]

im about to pull the goodwrench crate 350 (260hp) motor out of my 78 swb sport van and i plan to go through it thoroughly. I will remove the heads, check the cylinder ware, remove the valves from the heads for cleaning and inspect the seats and guides, all new gaskets, the 1102 summit cam, and a set of shorty headers. What im looking for out of this build is better fuel efficiency but also reliability. i would like this motor to start, idle, and perform like it did from the factory. Of all the classic cars i have been in (which are many), none of them seem to idle or start like when that car was new (even in stock form). Im only 24, so i dont know what it was like to turn the key of a brand new 72 chevy truck on a car lot, but thats what i want this motor to perform like. Assuming that the motor checks out, how can i make this motor like perform like new.