ok first stiffen up the chassis. subframe connectors, export brace, monte carlo bar, zray crossmember, add in torque boxes, add in stringers to tie the subframe connectors to the inner rocker panels, add in also the cross support that ties the two sides together into one rigid structure. remember the stiffer the chassis the more effective any
suspension modifications will be.
suspension mods, the shelby drop costs nothing and templates are available from a variety of sources, dazecars has the template in steel and he also has teh proper drill bit to get the holes sizes right. koni shocks on all four corners, proper springs front and rear. which ones you choose are up to you. and you will get lots of advice for choosing. run a 1"" or 1 1/8'' front bar, no rear bar, or a 5/8' rear at the largest.
engine mods, good heads, i have teh windsor jr heads in cast iron as they were the best at the time, but there are plenty of aluminum heads available these days and all are good. intake i prefer the edelbrock performer rpm with eitheran EFI set up on it or a 1406 edebrock performer carb, its 600 cfm and a damned good carb. for a cam again that depends, i got a retrofit roller cam from comp cams with the 351w firing order, but there are many good flat tappet grinds available as well, choose wisely. for headers i like the tri-y design, they fit well and shelby used them to great effect in the 60s when racing.
wheels, tires, brakes. i like the factory kelsy--hayes four piston calipers with factory rotors. they flat work. in the rear you can go with disc brakes from the aftermarket or use the F150 11x2 /14 rear drums, better tham what shelby used on the GT350s. wheels and tires are personal choice, but i plan on using a 15x7 steel wheel with either a 205/65 or 215/60 15 tire.
for a driveline, i plan on using 3.55 rear gears in an 8"' rear end and a C4 trans. what you decide is up to you as well.