Hi Chevy,

Congrats on joining the Amazon club! They are great cars. If I were you, I'd get the current brakes working first before you worry about a rear disk conversion. Unless you plan on racing, the existing brakes (assuming you have a disk front end) are pretty good.
The only issue I know have heard of with the drum rear end is the half shafts, which are tapered and know to brake under heavy race or rally use.
How much rust in the old girl? My main Amazon didn't look too bad, until I started to strip it to paint it, and then the fun (and cost!) began.
I like the sound of you engine. I'm in the process of building what sounds a very similar engine. Actually, a mechanic in Bathurst is doing it for me. What cam did you use in yours? I've been very tempted to go with one of the modern Swedish (Unitek or KGTrimning) ones, but I think I'll rely on what my engine builder knows best, which is the local ones.

JohnH