Tying the windshield frame to the roll bar "should" add "some" safety in a rollover. The main thing they add is the inability to run a half cab.
If you buy a trail cage that goes from the A-pillar to the windshield frame to the roll bar and tie to the frame you have added some safety. This is...
A buddy of mine brought his over to my shop last week. Purchased INOP in Fairbanks in 2002. Porthole windows were already there. We are getting it running over the next few weeks. Will ask if he cares to have partial VIN posted.
What axles are you swapping to? If other than CJ I would.
1) I see more of a positive feel in the front with the conversion.
2) No experience
3&4) No need for the full kit. You can buy just the shackles and new front spring, IIRC the Rubicon Express YJ conversion shackles add approx 1/2"...
My 33x12.50x15 KM3s came in yesterday so I spent a few hours cleaning the inside of the slots. Took them to my friend Tom (most OEM winner @ Sand Hollow 2019) and got them mounted today. Cant wait to get these on the 8!!