Seals and gaskets
 

Finally embarking on my motor build for the r car.

What is the current thinking on leak elimination at the various casting interfaces. Which sealers and gaskets, either aftermarket or newer factory work best in which application. I am particularly concerned to get the heads , barrels, cam carriers, rocker shafts, rocker covers the case halves and cam chain boxes and covers oil tight. ........ oh thats all of it :D.

Well, first of all, you should start with a platform that is at factory specs. I would send out the casing, heads and cam towers to a reputable engine builder and have the engine blueprinted. The process will eliminate the "tolerance buildup" in these types of engines and insure the types of sealants and gaskets can do their job effectively.
Sealant choice is been discussed ad nauseum so there are lots of threads on the subject. Gasket choices are pretty much Reinz or Wrightwood Racing. I prefer the latter. Their o-rings seem to be of higher quality than Reinz.