So I took the heads to the shop and the guy was very nice and willing to hook me up with a great price. He is going to remove the 2 sheered off exhaust bolts, clean the heads, install new valve seals and some LS6 springs I have. Also the guy is willing to mill the heads all for $200.

I need to let him know tomorrow how much to mill.

I am going with the Comp Cams Thumpr cam. Specs are:
Cam Style Hydraulic roller tappet
Basic Operating RPM Range 2,000-6,400
Intake Duration at 050 inch Lift 219
Exhaust Duration at 050 inch Lift 233
Duration at 050 inch Lift 219 int./233 exh.
Advertised Intake Duration 275
Advertised Exhaust Duration 295
Advertised Duration 275 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.553 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.536 in.
Valve Lift with Factory Rocker Arm Ratio 0.553 int./0.536 exh.
Lobe Separation (degrees) 109

I need to know what you guys recommend for how much to mill and what do I do for push rod length and do I need to worry about accessory alignment?

Engine Mods:
LM7, factory short block
Milled heads? 862 heads With LS6 Springs
Thumpr Cam
2" Primary LT headers, 3" exhaust with duel SLP Loudmouth mufflers
Edelbrock Performer RPM duel plane intake
Holley 750 cfm carb probably will do E85 conversion
MSD 6LS

 

I should mention that I would like to have around 11 to 1 CR

 

You're not gonna get 11:1 with those stock dished pistons. Even if you mill the heads .015" and used .040" thick Cometic head gaskets, it'll still be a tad more than 10:1 (stock is 9.5).

 

I would mill them 0.030 thousands,some guys have went as much as .60 I wouldnt go that much.Your not going to have much vacume with that 109 lobe sep.unless you run a vacume pump.Good luck with the build.

 

I should add that I didnt have any alignment issues going 30 thou.on my ls6 heads.I used 7.35 comp chromolly push rods but that was after i measured the length.I would measure the length first to be sure though.

 

I know you mean 0.030" or 30 thousandths (not .30 thousands). That is fine with LS6 heads, but not 5.3 heads. If you mill 5.3 heads .030", that'll give you 56cc compression chambers. I think you'll run into PTV clearance issues.

 

Yea I forgot.Your right batboy!Maybe 0.10 to clean them up a bit.

 

Went with 0.015, thanks BatBoy