so after overheating my 350 vortec and cracking some heads and the fact it was a used short block I am doing a full fresh motor.

I found a deal on some Large Port Bowtie Vortec heads and picked up a a Victor EFI single plane to run with them.

the new short block is getting some cast flat-tops to bump my compression up a bit over 10:1

Right now I have a comp XR258HR in it.

Since I am moving this from going into a DD into a weekend toy I am looking for more cam for these heads. I am running some GMPP 1.6 rockers.

So the Question....

The bowties do .530 lift. I have .600 under the retainer and seals.

To get more lift (like say in the .560-.570 range) can I do that on my stock length valves and LT retainers that are in there? Looking at the more aggressive grinds I am seeing that comp lists "machining required" but doesn't say what the issue is. Can I fit a spring under a stock length valve that won't bind?

I could maybe budget in some new springs and a cam but don't want to do longer valves springs and a cam.

And if anyone can suggest a decent grind that will work I am open to suggestions

Motor is going in my 1997 S10 with a T56 and 4.10 gears. Stock ECU is being dumped for a FAST XFI box.