Hey i was wondering if after the second set of cats could i just put a muffler and a turn down tail pipe on or would the loss of pip on my exhaust cool down my exhaust temp to much to soon and hurt my engine?
It doesn't matter at all. What you do to the exhaust after the exhaust manifolds(the collector), is not critical.
The whole exhaust is way too restrictive, too small for the given 302 V8. Any improvements in airflow are good things to do. Ignore any remarks about back pressure being a positive or needed thing. Back pressure is bad, it is never good.
The only gains to be had from scavenging(pulling exhaust from one part by another part(pipes passing each other etc)),
are done near the collectors(which are at the front of the transmission of these trucks). You cannot create meaningful scavenging past the collectors. That is, there is an ideal point to locate a cross over pipe, and only there can any slight gain be had from the cross over.
Check out any drag racing tech to read how that point is located. You will find that it's not feasible for most street vehicles to place that ideal cross over where it needs to go. Thus every vehicle you see with a cross over has it located too far back, too far to create any reduction of pressure at the cross over point.
So, open up the exhaust as much as you can, the only result possible is an airflow increase, which is very good. If you do a great job of improving airflow, you can cause the engine to need more fuel to restore the ideal air/fuel ratios. The computer is very good, but if you improve air flow enough, the PCM programming will need to be retuned, to add fuel because it's running too lean.
Any engine that begins to run too lean or too rich will produce less power, because it is no longer properly tuned. The goal should always be maximum air flow, and tune the PCM to provide the ideal air/fuel ratio. It just like modifying a carb'ed engine, you adjust the jets in the carb to obtain the fastest times(the ideal air/fuel ratios).