I have a set of 862 heads with the notch and I just had them surfaced.I didnt realize the notch thing on early ls engines so want to use these heads since I had some work done to them.I was wondering what head gaskets for this style of heads with 20 psi of boost.thanks in advance

 

Just weld the notch up and give them another skim surface.

 

The WS6 store sells head gaskets specifically for those heads. I used some on my first build.

Even with the correct head gaskets, mine started to push water at about 560 RWHP.

 

What you want for forced induction apps is the 862 heads (or any number) which can use the OEM metal gaskets.
A. Use an OEM metal gasket to fit that type of head.
B. Never resurface or modify the factory head casting from trucks
C. Prep the deck and head as per Service Manual using Acetone etc...
D. use brand new head bolts and never head studs with these type of heads
E. Allow as many as 100 heating/cooling cycles and 200+ days to an engine with NORMAL or Light boost driving (no high output) before raising the boost pressure to give time for the surfaces to get to know each other over half a year or so.
F. Always use a minimum timing when tuning the engine with the OEM gasket to minimize peak cylinder pressure.

Point of F: Power is meaningless in terms of gasket sealing.
I.e. You can make 500rwhp with a nasty cylinder pressure spike that blows a gasket, or you can make 900rwhp with a smooth cylinder pressure slope that does not peak as high and destroy the gasket. Power is an integral of torque over some time period, not a significant peak or related to the maximum peak pressure.

*note Avoid heads which do not use metal oem gaskets.