[Goat Blower]

I don't know of any overflow tanks that are fully sealed, most like stock have an overflow tube. I suppose you could cap that off on a Moroso aluminum can or something, but you'd need something to equalize pressure within the overflow tank, like a piston or somthing. A 20# cap is only going to raise your coolant boiling point. I don't see what that would have to do with the track. Jeg's or Summit will have a bunch of overflow tanks.

I haven't heard about any need for a diaper as of yet. If that's new for NHRA this year, most any universal one should fit. Again something at Summit or Jeg's.