I mounted an aluminum tank just behind the radiator.
This old photo shows the tank just in front of the alternator.
http://www.clubcobra.com/photopost/d...eng-1b-med.jpg
it works well and is very stable. It was going to be too much work to try to get it above the filler on the rad. so I allowed it to be a little below.
Looking for a spot to mount it seems to be more of a problem than anything else.
Hope this helps ( Hope the image show up)