You might take a look thru this thread and get some ideas what others have done.
http://www.67-72chevytrucks.com/vboa...d.php?t=612016
You can typically get away with a little more compression with the Vortec heads due to the combustion chamber design. Running a D-dish piston with a good quench will help as well. You need to calculate the dynamic compression to know weather the engine will run on your 93 octane pump gas or not.