Hmmm I took my vent tank off too, doesnt seem to harm anything.... but me after I fill up I smell fumes for about ten minutes after!!
As far as the plugs for the heads go I went with the pipe plugs, as a matter of fact I had one work it's way out one day to Seattle... scared the hell out of me I thought at first I blew an exhaust gasket but after close examination (after pulling over at a gas station) I found out what it was.
I went to the local parts store and got mine. If your looking for them still I got mine out of the "HELP" parts dept. You know what I'm talking about? The little section in most parts stores that have the HELP brand replacement products.
They have assorted size plugs and I found one that fits perfect, so after all was said and done I was very happy with the end result. Well just my two pennies.
Later
Husker