IIRC the gas filled ones are Wills-type rings - any idea who fitted them? I've not personally heard of anyone using Wills rings on a 200 block, as most (in as far as the ring type sealing method, as most people would opt for a WRC or Cometic type gasket nowadays) are either wire rung (solid wire used), or Coopers ringed (tend to go "jus' like that!"


http://www.yorkshirerallyspares.co.uk/ Click on Ford Parts, and you'll see they list Wills rings / gasket for competition Pinto - they might be able to help?