68 Firebird suspension questions

[Mowjo]

My 68 firebird is clean in appearance and runs well, however its suspension is tired, old and I'm sure somewhat unsafe. As I see it the first order of business is to upgrade from drums to discs out front but how far should I go with other suspension components and in what sequence? What should I do out back? My goal is to not only make it safer but to drastically improve the cars driving characteristics over the original.

Also how big of discs should I install? I'm interested in the Pontiac Rally II rims (16X8?) in chrome or billet to preserve a somewhat stock appearance... what size do I need to clear the discs? How bout tire sizes while we're at it?