This is my first rodeo with a Cleveland engine. Actually this build is for my 13 year old son to become his first car. I just finished a 1978 Trans Am for my oldest son, Rigell. That is the reason why performance expectations are low for the build. I would like the car to be able to run some 13's in the quarter mile while being dependable and pump gas friendly. My plans are to increase compression to around 9:1, choose a good camshaft with low to mid 500 lift and less than 280 advertised duration(hydraulic or hydraulic roller), and good aluminum dual plane intake. The heads will be treated to performance 3 angle valve job, new hardware to support camshaft, surface cut, and mild port and bowl work. It may get closer to 400hp before it is over.
Your expectations are a little optimistic . You really should run a minimum of around 9.7 compression and a minimum of 3.50 gears and premium gas to get close to your goal and 3.73 gears would be better . I would also use the bigger valves if you use those heads but if it were mine I would use big valve closed chamber heads and almost 0 deck it then set the quench/squish to around .036" with custom 4032 material pistons from racetec that mirror the combustion chamber . I would also have the heads lightly pocket ported by a knowledgeable cleveland guy . use stainless valves with hardened tips or one piece stock type valves but back cut the intakes . if you want a semi stock looking engine, the blue thunder or scott cook aluminum intakes are 2 good choices.
Below are the results from one magazines drag test of a 1971 boss from 1971 and they had around 10.0 compression.
4spd, 3.91, 0-60 - 5.8, 1/4 mile - 13.80 @ 104mph