Mark,

I am not the expert that Mike Shelvey or Todd E are, but I have done it on my 1970 T120 R a couple of times. The push rods should go back in the same position that they were in originally. Put a little grease on the bottom of the rod and you can tell if situated properly by feeling some suction between it and the tappet, Then turn the engine over (spark plugs out) until the push rods are at the bottom of their stroke and put the rocker box on. Use a new gasket between the head and the rocker box. Some folks use Yamabond.

Also, go on line and buy a Parts catalogue for your bike and, if you are going to do more maintenance, get a Triumph Workshop Manual. They are really good!