Woodies joinery help needed  

SDR, to be honest, if I were building that frame, I'd either use biscuits or just screw it together. For 8/4 thickness, biscuits, traditional mortise and tenon, half-lap (or bridle), or loose-tenon like Festool's "Domino" system.
As far as compressing the pins, sure, a drawplate would be ideal, but as long as some grooves are present to help disperse glue, it shouldn't matter much. You just don't want them so tight as to impede assembly or starve the joint of glue.
Accurately shaping a shallow concave surface like that in thick stock can be tricky. Depending on the curve, the typical strategy would be to bandsaw it rough and and then smooth to final contour on a large-diameter spindle sander. Hand tool alternative would be a drawknife and/or spokeshave (skills required, but no fossil fuels, loud noise, or dust).

Hi @glassartist - this is off topic, but I'm looking for drawer pulls and happened to see that you had some  around on this thread ( http://www.designaddict.com/forum/General-discussion/Good-Source-for-Mid...). I left a comment for you there too.
If it's not too much trouble, is it possible to upload pictures of them on that thread? I'll be happy to buy them off you (I'm in Singapore)
Sorry for hijacking this thread, everyone else!

All the alternate suggestions for type of joint and attaching methods are perfectly logical, but my goal is to reproduce what I see, even though none of it will show once upholstered. The only part I cant see is the pinning, hence the question. It had not occured to me that the upholstering substructure might not be original. Even though the fabric is not, The mesh matting, foam and straps all have the right amount of age to them for me to believe them to be original.
Actually the only thing I am changing is the base mounting braces ( one is visible in the pic). Unlike the center brace and end braces, the base mount braces are flat cut on the side that meets the base. So they are sort of bow tie shaped only with one side being flat. This means they are significantly thinner in the middle, which seems iffy at these important mounting points. I am making them wider (from 2" to 3") because my scrap of 5/4 oak allowed me to. Now if ! can only scare up a smallish piece of 9/4 (does that size even exist?) to cut the end pieces and center brace from.    Thanks folks for the solid dowelling advise.

If 10/4 stock is not available to you, you can safely and sanely make a piece of that stock by gluing two pieces of thinner material together.  If the joining faces are well flattened and mated the resulting log will be stronger than a single piece of wood.  And if you choose the material carrefully the joint may well be invisible.