ok, having spent the last 14 years doing a-body's, i have some tips.
all 87-76 mechanical bits interchange. k members, suspension pieces, rear ends, brake parts, etc.
since this is grm, ill focus on the performance aspects more than the resto aspects.
first step is to build subframe connectors. ive got some on my duster that i built from a guide at www.bigblockdart.com they really stiffened the car and made it handle better. reduced the number of creaks and rattles as well.
for suspension, assuming a small block, id get the 1 inch torsion bars and springs from firmfeel.com if money isn't that much of a concern, bill reilly has a setup for a 4 link rear, tubular upper and lower control arms, coil overs, and rack and pinion. really great setup, but it costs money.
for the money a good suspension setup would be
the previously mentioned springs
boxed lower control arms
volare/diplomat spindles and brakes
tubular uppers (i like the cap pieces)
adjustable strut rods
rubber bushings, mood problem solvers preferable
addco big ass sway bars
koni shocks
17 inch wheels.
8 1/4 rear from a later dart or duster
subframe connectors
firm feel stage 3 steering box
17 inch wheels from a bullit mustang with spacers to fit
id also go with either a stock magnum motor from a late 90's truck, with efi, or an aluminum headed small block. t5 from a mustang will fit with a lakewood bellhousing, different clutch disc, and some welding on the t-bar crossmemember.
rear discs from a jeep grand cherokee are rumored to fit.
the seats suck. toss them and use summit sport seats. your back will thank you.
use an aluminum radiator. the factory Chrysler units were adequate for stock, but are overstressed for a hot motor.
www.forabodiesonly.com
hope that helps.
and for my credentials, i present this:
http://www.pro-touring.com/forum/showthread.php?t=36043
michael