Yep. The guys I talked to at Burt Greenwald Chevy in Akron Ohio said that if you get the heads drilled out, you'll lose some of the performance gains that Vortec heads were designed for.
I don't think anyone is thinking about the aluminum ones right? The L31 cast iron ones are the heads that I went with. Got the Edelbrock intake, new valve covers, had to replace my roller rockers with stamped ones, new throttle linkage holder, spark plugs, etc. It was a lot of stuff to change, but I'd do it over again. I could tell a difference right away. They really complement my cam...and ever since I put 4.10 gears in, my Blazer actually hauls ass a little bit.
'73 K5
Chevy good...Ford bad