Been looking into doing the update front end on the old gal. Notice that the 99 turn signals look like they have 2 bulbs instead of one. How do I compensate for that. Also will I have any issues with how the body lines match up?

 

Electrically, just cut or add what you need or don't need. the bulbs are wired in parallel so it wont make any difference with one or 2 bulbs except for how much current it will take.

The bulbs are different as well as how they mount to the plastic casings. You may want convert that too.

The body lines are not quite exactly the same. The 89 has a more square line. I was going to do the opposite (98-88) but decided against it because I want my lines to "line up"

 

Pretty sure you need a header panel and front fenders maybe doors too.

 

Header panel and fenders I know I need to make my body lines look right dont think I need the doors or at least I hope not. I havent seen a 2dr with the newer front end on it. My turn signal lights mount to the light housing it just twists to lock it in. Not to concerned with the marker lights since Im comp cutting the fenders up front as well as the front header panel. Will I need the front bumper as well or can I keep my stock one?