Need Full Exhaust System on an 84 K10

[SourTooth307]

I checked out Summit Racing and found a Thrush header-back dual exhaust system (#89024) for $248, a set of headers (#SUM-G9014) for $180, and a universal fit Flowmaster cat (#2900225) for $64.

Now, I'm trying to do this without going too far over $500 so what is the best way to go about this without robbing my truck of too much power? Should I do Y-pipes thing with two mufflers, Y-pipes with one muffler and dual outlets, or just do the true dual thing with two cats? Also, if I do go with the Y-pipes, how much of that exhaust system ends up going to waste?