ARP Head Studs.
Factory head bolts are one use only (torque to yield). ARP studs can be reused. (231-4701 is the ARP part number)
Factory head bolts are about $80 for a full set. You will still need the four short bolts (GM Part number 24407225) even with the ARP kit. You can find these online for about $5 per bolt or about $20 for all four. That means the other 10 bolts cost you around $60.
The ARP studs are around $160. They are about $100 more overall but are reusable and hold the head down better than the OEM bolts. For $100, well worth it. If you're having a speed shop do the work for you, they may offer a discount on the ARP studs if they have better buying power than you.
While not really a "mod", I would also look into changing your timing chains. 70K still is pretty young for a timing chain (and most cars go well over 100k before "needing" one...I went 150k on my LE5 and it was still good) but if you want a little piece of mind, now would be a good time for changing the timing chain and it's guides. It's already off to get the head off and change the gasket so you're saving on labor.
Other than that, a quality head gasket is the only other thing I can thing of. You could do springs, and titanium retainers and an improved intake cam that overdrives the high presure fuel pump (HPFP) and all those will give you benefits but only if you're planning on doing more power upgrades and have a bigger budget as these parts can run a few hundred dollars each (Other than the head gasket).
TS brings up a good maintenance procedure to perform now (though I wouldn't call it a "mod" either), the LNF turbo engine doesn't have fuel pass over it's intake valves and thus they are very prone to carbon buildup. Since the head is off anyway, now would be a good time to have that cleaned up.
Last edited by Robotech; 09-17-2019 at 05:54 PM.