Many years of this stuff! I also did this exact build-up in two articles I wrote in the Hemmings Mustang Mag, and on the Mach 1. Funny thing, the Mach had rust problems, and Chepie's structure was solid. I bet chepie could have kicked the Mach's butt in the twisties! But now, the Cobra would just have annihalated them!
Heed the advice given by these guys, it is invaluable. I did exactly what 5.0in66 talked about. I thought my car handled poorly so I overhauled it. Upper and lower control arms,polygraphite bushings, tierods and idler arm, dr gas variable-rate coil springs, 4 1/2 mid-eye leafs with new shackles, 1-inch sway bar, kyb's...etc. After all was said and done, guess what.....my car still felt like crap because i didn't properly address the steering (i.e. the box itself). Chepsk8's advice is probably the best thing anyone could've told you right now, mainly because you still have your cash. Defintely take the time to properly diagnose what actually needs to be replaced. If I would have thought things through I probably could have achieved my goals with just a flaming river box and some cheap weld-in subframes. Money is an extremely limiting factor for you right now and with such a strict budget you may be better served to just chill out and save until you get ahold of some more cash to do things right. I know i wish i did Good Luck
don't forget about sub frame connectors, dollar for dollar those will be one of the best improvements you can make.
like everyone else has said have a plan. if you are one such a limited budget you may have to do things in stages.
first make sure the rest of the suspension and steering system is in good working order, tie-rods, idler arm, pitman arm, center link, steering box, ball joints, etc. if anything there is not up to spec then doing these planned mods will be a waste of money. if everything seems up to snuff. then i would do as follows.
1) shelby drop and bushings
2) leaf springs
3) coil springs
4) subframe coneectors
5) monte carlo bar and export brace
it would be best to do all of this at the same time because any of these could change the alignment settings to some degree, the leaf springs and subframe connectors not so much but could if the rear suspension is sagging badly