Welcome to the site. Cars look great
First off, you'll want to clear those corners. You'll hear that a lot on here. It's not too hard to do and you can paint the bezels or leave them as is.
As for modding the 3400 motor, you'll want to check out
www.wottech.com It's all performance parts for the 60* V6 motor that you have there. The guy that runs the site, his name is Ben and he knows his stuff. He's got performance parts for 60* motors as far back to the early 90's late 80's motors. I have his manifold set and just bought his 3500 valves. Going to buy valve springs soon too.
The lowering and suspension. KYB GR2's are probably the best right now. PFYC carries them in a set for $270 or Summit racing sells them singles and a set of 4 would be $238. I need new ones so I've been looking
Give a pretty good ride. Been very happy with them. As for lowering, that's up to you. Eibachs give you a 1.2 inch drop. That's what I have because the roads in Philly suck and I bottom out sometimes. There are also Intrax which give you a 2.2 inch drop. I would suggest getting the camber adjusting bolts with lowering the car. 1 set for 1 inch, 2 sets for 2 inch.
As for the HUD, I don't think anybody here has tried it and HID's, some guys have them, I'll let them tell you about that
Keep in mind that the L36 you had is a different motor than the LA1. The L36 is a 90* motor and the LA1 is a 60*