No, not true. If you try and have them ported, there’s not a lot of meat to remove to improve the head. They’re fine as is or bowl ported.
Type into the YouTube search, Charlie Servedio, he’s porting magnum heads right now.
I run a bone stock 2003, 5.9 long block with a RPM AG intake, Edel 750, MP distributor with a Chrome box and Hooker 1-3/4 headers into a 2-1/2 exhaust. Excellent driver, go anywhere, rock solid. Backed by a mild 2500 stall converter & 727 w/a 9-1/4 rear w/3.55 gears on 245/60/15’s.
I myself wouldn’t increase the compression. I’d even drop the bone stock ratio down .5. It’ll run on 87 if you use a carb. (I know you’re not, that was for everyone else.) or run a larger cam to drop the dynamic compression a tad for 87 octane.
The best thing about the fuel injection is how well it runs and how nicely it keep the cylinders even after many many miles. A small roller would work very well