Searsgremlin

Ok so, I recently got a 260z bone stock, also my father owns a salvage yard and a 78 280z came in pretty much complete so its like a parts car. After that i traded some interior parts off the parts car for a 260z motor that has a header and a set of wheels. i picked up the motor and it turned out to be a 240z motor with a e31 head on it. i want to build up my 260z motor a little. i plan on putting weber dgv carbs on it along with the header. My brother works at a motor building shop so i was going to have the e31 head planed, ported a little, polished, and put bigger valves in it. is this going to make a big difference in the performance and will my compression be to high to run pump gas? also what difference will the carbs and header make?