The 4.3L engine production started with the 82 model cars and ended in 85. If production had continued in 86 there was plans to put the engine into the FWD 98 and 88 body styles.
In 82 both RWD and FWD used cast-iron heads. Appears that the aluminum heads were used in the FWD cars starting in 83. The engine is quite heavy for the FWD car and they tried to cut weight down with the lighter heads and using an aluminum hood on the car also.
The RWD cars were equipped with dual batteries, the FWD came with one large battery. Two types of starters were used, the Delco-Remy unit and the Mitsubishi. The Mitsubishi is smaller, lighter, and more durable from what starter repair shops have told me. Both starters will with the 350 and 4.3L, although the Delco maybe to large to easily fit in the FWD cars as space is more limited.
They did not use the hydro-boost master cylinder as with the 350, the vacuum pump provides enough vacuum to operate the power brakes.
The 4.3L's use a belt driven vacuum pump, which is similar to unit used on the 350 which is operated off a shaft from the oil pump.
The RWD 4.3L uses the same air cleaner housing as the 350, the FWD engine has lower profile unit due to engine compartment size.
The RWD and FWD engines use an electric in-line fuel pump which is located just before the fuel filter. Unless the car was expected to be used in warm climates the engines also include an in-line fuel heater which operates when the fuel is below 20 degrees and is suppose to warm the fuel up 20 or 30 degrees.
I did have one time in 1984 when my fuel was not winterized properly and the car would not run because the filter waxed up. It was well below zero at the time. The block heater was plugged in so the car would start with no problem, but fuel supply was cut off at the filter even with the in-line heater.
Changes were made in some of the emission control items during production years. In 83, they made low altitude versions and high altitude engines for the western states. I drove my car to Colorado one time and it was overly rich in the mountains. Extreme black smoke and could only make uphill grades with trans in 2nd at 35mph. Car made it to 14,000ft and still had plenty of low speed power. In 84 or 85 they added a feature that advanced timing 2 degrees at higher altitudes.
The 85 engine added some minor computer controls for the diesel. A change was made in the head design part way thru the 85 year and head gaskets are different. No listing is available for any head gaskets in 85. Hopefully if anyone has one it is before the change or else plan on custom made.
I have noticed the 4.3L's have higher torque on the headbolts then the 350's and might assume it was from changes picked up learning from problems with the 350.