Some of the changes from the Gen. 3 to Gen 4
1. More travel, from 17" front to 18" and 18" rear to 20"
2. New style airbags w/ rubber bumpers internal to the bag
3. Uniball trailing arm pivots (from Derlin bushings)
4. Longer axels w/ 5.5" backspace wheels so car will still fit in a trailer
5. Better power steering rack.
6. 4" longer wheel base
7. And a bunch of cosmetic stuff
8. Midboard hubs (12 bolts) on the Gen4 instead of microstubs (3 bolts), which accomodates the longer axles to allow for more travel without abusing the CVs.
9. Better radiator setup, uses a cradle instead of hardmounts
10. C&R radiator instead of Ron Davis radiator
11. A-arms are bigger tubing, heavier duty
12. Larger front spindle axles
13. The overall length is about 6 to 12" longer than Gen3, depending on Subaru or V8
14. Bigger gas tank, hold 3 more gallons
15. Cast iron rear suspension pivots
16. All cars have Uniball pivots on the rear($250 option)
17. Gas gauge for gas tank, instead of visi-gauge mounted on tank.
18. Billet rear view mirror