Hi Mike, we used the Bus Depot one.
http://busdepot.com/details.jsp?partnumber=352000on our 78 bus and my brothers 78 westy.
Seems like good quality, pretty thick metal. Should last a good long time. On my brothers, we needed to spread out the 2 ends that connect to the heater boxes on the muffler about 1/2 inch in order to get them to line up properly in order to bolt them on, but other than that, works great and runs nice and quiet.
All in all, very happy with both.