I done both when I did my current mill.Just remember all of the costs when stepping into a basic EZ head It wont end with "just heads" whoever sets your heads up(do not just buy them from Indy and bolt them on)will recommend a valvetrain and cam setup when you decide which heads you want.I would stay with the top end you have and get that heavy,old rod and piston set,possibly cracked crank,and get a good base for your new heads for next season
Gus