68 camaro convertible suspension- need help

[LV42DAY]

i have a 68 camaro convertible and i will be ordering several new parts and i will be needing a little help with the suspension for a pro touring stance.

the car right now feels like its floating and the rear leafs are sagging one side lower then the other by over an inch. the car has been sitting for what feels like an eternity but i am trying very very hard to get it on the road within the next few weeks.

i already replaced the body bushings and transmission mount when i install the new 700r4 to energy suspension polys.

the parts i plan on getting will be:
summit racing brand 1 1/8th front sway bar
energy suspension sway bar end links
addco 7/8 rear sway bar
energy suspension control arm bushings
energy suspension motor mounts
summit racing brand 2" lowering leaf springs
qa1 single adjustable front coilovers

my questions:
its a 68 convertible with a 400 sbc with aluminum heads and a vortech supercharger, power steering and no A/C, what size spring should i use with the qa1 coilovers? they come in 250, 350, 450, or 550 springs.



for the rear sway bar, i plan on getting a four link in the Fall season and was wondering if i will be wasting my money if i buy this now? will i still be able to use it with the four link suspension or something similiar to the four link (i'm still undecided what direction i want to go on this). with that said, i am definitely getting the leafs now since they are sagging so badly and i cant put money towards the four link until the car is at least on the road so i can make sure everything else is working properly.

im am completely open to any suggestions, such as parts i should also add or parts i dont need etc, as i hate wasting money by buying things twice.

long term plans: four link, subframe connectors.

if i hit the lottery long term plans: full frame or new subframe and 1 piece rear frame (integrated subrframe connectors)

thanks in advance, geno