Welcome, nice looking van,
The front end is the same as the cars except the controls arms are braced. The bushings are not a bad job and worth it.
I wouldn't go 20/50 but 10w40 or 5w50, I run the latter and my engine is fairly new.
I would just go over it and fix all the little stuff, it all adds up. You need to figure out your goals, if your going to drag race, or just want more power. Intercoolers are always a good idea. The turbo you have is your cap right now, to get any type of performance, it has to go. I would go to
www.thedodgegarge.com and read the turbo database section a few 100 times. It will give you the basics and answer a ton of your questions.
Lowering, use Daytona front struts and cut the mini coil springs. Rear, you can dearch the leaf springs or another member made custom shackles. 2 inches is all you should go. After lowering the rear, you need to adjust the brake compensator, if not, you'll lock up the back end on the slightest brake application-ask me how i know,