Some parts are, the 2.7liter is but some of it's electrical components are not
what is compatible with what?
That depends on what size engine you have. HOwever, most Jeep Cherokee/Grand Cherokees had compatible parts from 1984 to 1998(1). (1)Chilton Repair Manual
At least some Aerostars (like the 1990 3 liter) do not have an EGR valve, they use a 3 way catalytic converter.
Perhaps a small handful of interior or drivetrain parts, but the practical answer is none.
5/30 will get in between the tight moving parts
Not likely. The transmissions are different. If you own a 1990, you can use parts from 88 to (I think I remember this correctly) 92.
You can try to find 1990 Dodge parts online. There are many auto parts manufacturers online selling their parts.
Yes it is!
The starter is interchangable between all 1990-1994 Legacies and maybe even up to 1999.
The 1990 Chevrolet S-10 shares parts compatibility primarily with models from 1982 to 1993. Many components, including engine parts and interior fittings, can also interchange with the GMC S-15 from the same era. Additionally, some parts may be compatible with later models up to 1998, especially for suspension and drivetrain components. Always verify specific part numbers for the best fit.
For a 1990 Isuzu pickup, several parts can be interchangeable with other models from the same generation, particularly those from the Isuzu Trooper and Rodeo. Components such as engines, transmissions, and suspension parts may be compatible. Additionally, some body parts like doors, fenders, and hoods from other Isuzu models from the late 1980s to early 1990s can also fit. Always verify specific part numbers and consult a parts expert for the best match.