Injection all the way. !!!!
I would suggest for the A15, to leave the cam if your on a budget, as on the a series you have to pull the motor appart (not just the head) leave that for when you do a full rebuild inc pistons etc. Go with some nice fine tunning like said below, electronic fan, electronic fuel pump, electronic dizzy and max air flow. then start on the head work like a gasket match for the inlet and exhaust. This opens the doors for some nice mods, like larger valves, double springs etc