All good stuff, thanks for posting
Here's a GMT400 1998 2x4 C1500 5.0L regcab PU w/ GVWR 6200# and front GAWR 3600#. Its front GAWR is ~1100# greater than the Roadmaster Wagon (w/ front AGWR 2532#). Percentage-wise, that's a big increase in front GAWR.
Here's a for GMT400 1995 4x4 K1500 5.7L excab PU. GVWR 6600# and front GAWR 3925#.
It's not a proper comparison for this thread because it's 4x4 w/ the IFS front end, but notable all the same.
It's interesting to see the difference in GVWR and GAWR between these and your '88, GVWR 5600# and front GAWR 2950#, and the Roadmaster wagon GVWR 5781# and front GAWR 2532#.
Of course, I've been using the Roadmaster Wagon for comparison b/c I believe it uses the same front UCA and LCA as the Impala and other B-bodies, the subject of this thread, and possibly the D-body Caddy Fleetwood Brougham
the cadillac hearse is something worth looking at too, they used bigger brakes, larger hub, more beefy suspension components. I believe GM called it their Commercial Chassis
Here is something on the cadillac D body towing package
The 7,000 lb. trailer towing package was made available 1993, something not seen in a production sedan since the 1971–1976 Cadillac Sixty Special. The RPO V4P package included
heavy duty cooling (RPO V08, which consisted of a seven-blade mechanical fan and an
extra capacity radiator), RPO FE2 Suspension System Ride Handling,
HD 4L60 transmission,
RPO KC4 Cooling System Engine Oil, RPO
KD1 Cooling System Transmission Oil,
RPO KG9 140 amp alternator, and RPO GT4 3.73 gears with an 8.5-inch ring gear. In 1994–1996, the V4P package was revised with RPO GU6 3.42 gears with the new more powerful RPO LT1 260 horsepower (190 kW) V8, and HD 4L60E transmission with unique accumulators to shift smoother with the shorter rear axle gearing.
So a bigger alternator(CS-144), Trans and oil cooler (auxillary), bigger radiator, a firm handling suspension(bigger sway bar, stiffer suspension I assume, just guessing) and a HD 4l60 which was probably a stronger case casting or maybe even internals upgraded.
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Heres a bit on the roadmaster:
Ordered with the towing package, the 94-96 Roadmaster was advertised to tow up to 5000 pounds, although the Estate Wagon owner's manual extended that to
7,000 lbs. when using a weight-distributing hitch, dual sway controls, increasing the rear tire pressure to 35 psi and disabling the Electronic Level Control. The tow package added 2.93 gears and a limited slip differential, heavy duty cooling system including oil and transmission coolers, and a factory installed self leveling rear suspension consisting of air shocks, a height sensor between the rear axle and body and an on-board air compressor. The most distinctive feature was the combination of one
conventional fan driven mechanically from the engine alongside of one electric fan, offset to the left (non-tow pack cars came with two electric fans).
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on the subject of the lower control arms
It seems like the 96's had a bigger ball joint than others, and commercial chassis/d body had a measureable difference but it sounds like they should still "bolt on" which may be closer to what you want for a truck. Cadillac commerical chassis was mostly hearses