on the one hand you say "no need to go larger then 600cfm" then on the other you recomend goin with a 800cfm tq??? hmmmmm.
Most Engines that use a Vac. Sec. carb will only open the secondaries as much as it needs.
one other thing, the 50lb stock TQ intake with a 800cfm TQ will run rings around a Edelbrock perfomer intake w/ a 600cfm eddie carb.
as far as cams nothing wrong with the stock 340/360 4bbl cam. works with practically any cr and performance hop ups.
exhaust manifolds are nice, but a set of 1 1/2" to 1 5/8" headers with 42" primaries into a 3" collector will work wonders.
no need to get fancy pants on the ignition system either. the stock MP electronic pkg is more then adequate.
cheers.