After moving house I am rebuilding my brewing apparatus from scratch. I started with the MLT. Nothing too out of the ordinary here, but somebody planning a similar conversion might be interested in my design choices.
I used a 70qt Coleman Xtreme cooler
, which is very good value for the size. I found that a 1/2" close nipple was just the right length for the bulkhead. I had bought a 2" nipple but it was much too long. I reused the plastic washer from the cooler drain to seal the inside of the bulkhead, and strengthened the cooler wall with a section of PVC pipe as recommended by Bobby M. The bulkhead was rock solid and sealed watertight. My thanks go out to the folks at Home Brew Talk who pioneered this design.
I chose to make a 4-tube copper manifold with 1/2" slot spacing. The shape of the manifold is conventional, but I improvised a sliding tee arrangement to connect to the drain.
There's a few more picture on my blog page
, as well as assembly instructions and a parts list.