I originally read about this kit being available on the 6-Pack Forum.
This is the link to Justin's site and the product page and prices follow:

J.M Wagner Sales, Limited

This is what you will receive when you order the gasket kit for the TR6.
The original cork gasket is shown for comparison only.

The new silicone gasket is formed to the shape of the cover with an inside lip.

As you can see, there is a lot of difference in the thickness of the two gaskets.

There are cut outs located on both ends that must be placed on the left side of the head.

First step is to remove the valve cover and clean the mating surface of any oil or old adhesive. 

If these areas aren't clean and dry, you may have sealing issues down the road.

The instructions state that the gasket should be laid down and trial fit.
Notice the cut outs on each end for the head bolt?  They favor the drivers (left) side).

It looks to be a little short, but it will stretch out after you fit it to the valve cover.

So there it is, ready for the test fitting of the valve cover.  I am following Justin's blue book.

Now's the time to get the gasket fitting inside the cover properly.

Now we're back on the bench for a look at how it fits inside.  Also remember that
the cut outs go to the left side of the engine.  If you do this wrong and glue it down,
Justin clearly states that you will need a new gasket to correct your error.

These pictures were for my benefit as well to look back and remember what I did.

This is the little blue book that I've been following.  Cheaper than buying two gaskets!

This is explained well enough for me to even do it correctly.

I started with the 3/16's" of silicone sealer all around the outer lip of the gasket.

Next 3/16's" of sealer on the same groove where the old cork gasket would have lived.

Nice and neat. so far, but you do get to get messy on this part.

This was not in Justin's little blue book, so I did stray from the instructions a little bit.
It makes the smearing of the sealer inside the cover into a thin film easier and
keeps your finger clean throughout the process and from getting sealer on everything else.

Now the cover is on and "slightly and evenly" fastened down.  You should see
about 1/4" of gasket all of the way around the head.  Make sure that you do at this time.

OK on the right front corner.

OK on the left rear corner.

And OK down the left side and around the corner.

That pretty much wraps it up for the next 24 hours.  At that point the cover can be
tightened for the final time until it begins to slightly bulge, then back off.  That
should complete the installation and the engine can now be run.  All of the other
care and precautionary issues are covered in the all encompassing little blue book.

All in all, a very nice product, well documented and all parts are included in the kit.

J.M. Wagner Sales, Limited
1613 Chelsea Road, Suite 145
   San Marino, CA 91108   U.S.A.