Before you drop a bunch of money install a set of rear 4" drop springs and pull your front springs and cut 1 coil off and find a factory front sway bar . , That should give you a 2"/ 4" drop and cost less than $125.00 . drive it and then decide if it works for you or you want to go lower and spend more $
Once you start going lower you'll need a lot more parts and time , $ . When you decide to go drop spindles with disc brakes and lower rear springs you'll also need new ball joints ,etc etc thats when it all starts .
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1967 Factory short bed - Old school
'71 - 350 / 4bolt / 487 heads / Edelbrock C3BX
Muncie M-22 4 speed / Hurst Comp plus
Factory 12 bolt posi 3.73 / 255-70-15
Smoothed firewall / Factory cowl induction
Power disc brakes / power steering / 3.5-5" drop