first off i think on my left bank of cylinders, near the back whenever i get on the gas to get up to speed, i can hear a ticking/whistling noise, but it wont do it at idle. if this is a head gasket problem, should i go ahead and replace both?
now my converter, anytime i go to start it, or accelerate(1400-1600 rpm's) i hear this dreadful knocking coming from it. would i be able to take out sed material thats knocking and reuse cat? or could i just buy some 2 bolt flanges and a chunk of pipe and straight pipe it? would that hurt my overall performance? considering still have a flowmaster muffler on there?

Mere opinion here, but I would say the ticking and whistling you are hearing is an exhaust leak, not a head gasket. Could very well be the exhaust manifold gasket.
As for the converter, I haven't a clue what the noise is, however if you were to just take it out and run straight pipe that could open up a whole can of legal worms... If I were to go with one of the two options, I would take out sed material and reuse the cat as pipe. However that can have its problems, also... I am not sure it would ruin your performance, but whole system is built to work together and you could end up with other problems...

i looked at some magnaflow high-flow cats. one is 144$ and the other is 244$. stupid question but what would be the differences?

i do to think its the manifold gasket, but if i replace one should i replace the other as well?

i looked at some magnaflow high-flow cats. one is 144$ and the other is 244$. stupid question but what would be the differences?
link to the products?

i do to think its the manifold gasket, but if i replace one should i replace the other as well?
from a preventative maintenance standpoint, you may as well since you're down there.

its not the manifold gaskets, everything was caused by the catalytic converter, there was a small hole in it, as well ans cat material knocking around inside of it. so im getting that replaced next tuesday or wednesday