I have 500 efi motors getting new valve springs. We took the headers off and I found the gaskets for these but noticed the rubber couplers for the silent choice are worn. I can't find these yet. Looks like a 4" plumbing rubber coupler with hose clamps, or do I buy exhaust hose and cut to length? I just figure there has to be something specific to these. Also anyone seen where these couplers bulge/ballon inward to the joint?

You talking about the bellow between the tail and Y-pipe? Double check - They make a bent one and a non-bent one. My CMI tails require the bent one.
http://www.ebay.com/itm/Lower-Bent-4...0d2364&vxp=mtr
And yes they will bulge at the bend and eventually blow at high speed. Don't ask how I know...

Thats the style coupler but looking for the upper one. Connects to the thru hulls and the y section the solenoid mounts on. Blow out is exactly what I want to avoid, lol