Comp Cams and probably others have +.050" locks and/or retainers that can provide extra installed height and, naturally, extra coil bind clearance as well.

If by "stock valves" you mean the OEM material with multi-groove locks......don't do it! You need the extra durability of stainless, multi-groove locks reduce your strength, less flexibility with installed height and they flow worse. Nail-head intake and tulip exhausts tend to be the best combo. You can use longer stem valves, but you'll have to check the rocker geometry - contact & sweep.

Have the heads been ported within the volume specs?

That's a pretty small cam for SS? I found some stiff beehives from Comp for my Stocker cams which might help with spring clearances as well as rocker clearance - if they have enough pressure & rate. 26056. But it probably won't be enough & I run a lot less lift.

I like and appreciate your efforts. But you can only compromise & budget so much.