Car is an 83 Z-28 with a 350 with nothing major really done to the engine yet. I had an exhaust picked out that was over a grand and decided to build more of a budget build all around on the car. The whole exhaust would be:

Hedman 68470 street headers $151.95
Hedman 17478 matching Y Pipe $119.95
Walker Exhaust 15032 Super Converter $57.95
Dynomax Performance 17495 Turbo Exhaust $193.95

Total System $523.80

My questions are will this system work together for one and if not what would I need to change. Second would I need to do any welding at all or would I be able to just clamp it all together. Appreciate all the input....

Wherever 2 parts connect, like the y-pipe to the cat. Your either gonna need flanges to weld on to bolt them together, both them directly together, or a way to expand one side to create a slip fit then use clamps to hold them together.

I think I've seen these long-ish sleeves, that allow 2 pipes to be joined clamping them together, without expanding them, but no idea who makes them.

I used those Hedmann Headers & Y Pipe, and they fit relatively well. I had to do a little creative coupling with the Y Pipe and headers, but I also had the Elite coated headers, there may be a difference but I don't know why. There are 2 Y-Pipes, the 17478 and the 17470 - call Hedmann direct and find out what the difference is - they both state they are for the same headers - maybe that's where I ran into trouble.

The headers and Y Pipe come with adapters and clamps to connect together and to the cat, assuming you use a standard size cat (2.5 inches).

I stuck with my old cat, but gutted it, and used an Hooker Aerochamber muffler - supposed to be good flow on the Aerochamber and has a nice sound without being loud like most Flowmasters I hear. It all seems to work fine on my 350 carb with stock I-Pipe.

Check into special ordering at local AutoZone or Advance - they order alot of aftermarket parts, usually cheaper than summit, usually gets there in 2 days max, and is totally returnable without shipping expenses.

On Summit, the Hedmann headers, Y pipe, and Hooker Muffler add up to +/- $350, and gutting the cat is free!

I dont usually plug anyone elses products but if your'e looking for great exhaust tone, Holley Aerochamber or Classic Chambered Exhaust. Had both, but since my exhaust is running straight now and with space constraints I decided to try the chambered exhaust. It sounds niiiice, and not rasp when letting off the gas after hard acceleration, its great!

So I don't think anyone has commented on the cat-back from dynomax or if my cat-back pipes are not bad now should I just replace the muffler or is the old tubing to constrictive? Appreciate all the input so far...

If it were me, and your current I Pipe is still in tact, I'd leave it. You said your not making bookoo hp right now, so the 2.5inch I Pipe you have should be plenty sufficient.