Longer pushrods are only used when changes in valvetrain necessitate their need. I have not seen anyone here that would need them except maybe something Pontiac Jeff might do with milling heads etc.
If you deck the heads enough, then pushrod length changes come into play. Certain rockers require different rods and come with them. Stock rockers, need stock length rods if the heads have not been messed with.
Oil restricted rods should only be used where needed. Many have changed ways of thought to not using OR rods with roller rockers due to some failures and premature wear they have experienced. Oil is a lubricant and should be allowed to flow whenever possible. You need to keep oil flow if you stay with stock rockers.
Adding an oil pressure increase kit is well worth the cost. I recommend them for every motor I work on at this level.
Double chain'* have been getting a lot of breakage lately. Do a lot of research before you choose one. It also introduces a ton of vibration into your drivetrain. As an example of how much vibration it makes, I am running a single chain. With Stage 3 heads, 130# springs, S1X cam and 1.8 rockers on top of it all. .579 /.592 lift. Justin..you saw/felt it. Single chain was my choice. In addition the vibration will give your motor mounts a beating.
00 Regal GS: All kinds of cool stuff.