EASIEST Horsepower is going to the Vortec heads ($400-500 COMPLETE). with a edelbrock performer and these stock heads you got 50 hp right there not to mention you have NEW heads! Your motor could probally use a valve job anyways this will just save you the hassle .......Take your camshaft and retard it 4 degrees and add some new 1.6 rockers and you will get your 70 horsepower (or damn close!) for probally about $700.00. Here is where I got mine. They have some good info about them too.
http://sallee-chevrolet.com/Cylinder_Heads/Vortec.html

Bad-Habit