Can someone tell me the benefits of the following mods, how they work exaactly and whats involved in the install?

Mods in question: 1.9:1 HS roller rockers and 105# valve springs

Stock rockers are 1.6:1 so installing 1.9:1 rockers will open the valves further and a little bit longer. This allows more air to move threw with less effort. Stock valve springs are 60#, so installing 90# or 105# springs allow the valves to close faster, this is needed when running at higher RPMs such as 6000 rpm shift points. With stock springs you risk valve float.

ok makes sense. So what is involved in replacing those? I imagine the sc has to come off in order to get to the rocker housing yes?

Nope, Valve covers are all you need to get to the rockers.

Rockers are one of the easiest things to change, springs are a bit more involved. Here'* a write up.

https://www.gmforum.com/t278815/

THanks guys

Yep...look up. Dan linked ya.

Is there any tuning needed with this mod, and /or supporting mods that would aid in performance?

Tuning will help, but not needed. Rockers, springs, and pushrods all go together. Pushrods are optional.

Good deal. I've said it before, u guys are clutch. I may actually do this mod after i finish my pully swap.