[Healeys] Timing chain tensioner

[ggilliam at usol.com]

Hello Listers, Happy Halloween!

I am working on a 29K engine, and among the parts I'm replacing is the 
timing chain tensioner. The Moss replacement I received is a spring 
loaded unit, as opposed to the oil pressure operated original unit. 
Anybody have experience with this item...good or bad?
  There are also 12 small o-rings in the head gasket kit...for valve 
stems I presume?
How are they used? They were not present on the head at tear down.
Regards,
Gordy