I would say it depends on when and how far you plan to build the truck....if you are going to a bigger charger in the not so distant future, you will probably need a WG...if you do the exh manny and up pipes now, you will have to back into the up pipes if you do a WG. I admit I might have a biases because I am regretting not doing a WG while I was in there. I did the 71, ported intake, and 6.0 exh manny with up pipes all at the same time so I don't know how each on by itself affected my truck's performance.
With that being said, unless you think it will be within next 6-12 months, I would probably lean toward the exh manny/up pipes...like someone said earlier, the up pipes are known to fail which seems to be hit and miss. They should help you run a little cooler and with all of the piston issues as of recently, I think trying to run as cool as possible is a plus. Of course, a ported intake manny should at least theoretically reduce the risk of cracking the rear pistons...but it seems like the back 2 aren't the only ones failing.