There are a number of guys running all stock suspensions with a lot more than 500 hp at speeds over 140 mph in the quarter, so the stock stuff is plenty capable if you set it up correctly. It also doesn't take much work to make them corner better than they did in the 70s. Radial tires and a modern alignment go a long way towards improving that.
Most economical brake approach is the factory 11.75 discs up front with at least 10x2 drums on the back. Unless you are hitting road courses with multiple braking moments at 100 mph plus, this will be more than adequate for any street/strip work. If you want to lighten things up, then a Wilwood kit may be helpful. 0-100-0, you planning some Ultimate Street Car type stuff? If that's the case, then you certainly need to consider larger diameter rims with a bigger step up in braking capability.
The $4000 front end kits you're looking at are nice in that they will help drop weight off the nose, but they are not a requirement for better cornering or faster e.t.s. Figuring most of these will shave 100+ pounds off the nose, using them means you are paying around $35 per pound to loose the weight. Is the weight important? The coil over set ups do allow for quick spring rate changes, if that is a requirement you have. Otherwise, the stock set up with offset upper control arm bushings more caster for high speed stability will be plenty safe. The caster/camber trade off in alignment is probably the biggest failing of the stock mopar set up. Add in some good quality adjustable shocks and you could have a safe, reliable stock style set up for a few hundred bones, assuming it is already in good conidtion.
Out back is a similar situation. If this was a dedicated drag car running on multiple tracks with widely varying traction conditions, a four link or ladder bar set up would allow you tuning flexibility while planting the tires. As a street/strip car, the factory style leaf spring set ups are dead nuts reliable and can be tuned to hook up with slicks with only minimal effort. The drawback to leafs is that they are heavy and swapping rates is not easily accomplished. You can save some weight and add some tuning with a Cal-Trac set up using a monoleaf that bolts in to all the stock locations.
If you really want a lot of aftermarket visual appeal, talk to Bill Reilly at Alterkation. They have both front and rear set ups. There also is XV, but their products tend to be slanted more towards road race capable set ups than drag racing. Cal-trac has rear set ups with a more drag racing slant. There are a few others out there, but their names slip my mind right now. Firm Feel has a number of parts that could help in yoru goals, but they tend to be oriented more towards stock style, bolt in replacement parts.
