If I had a extra $4k to drop on my car... I would probably try and find or make better suspension... struts and independent rear suspension... EFI... a/c (done properly)... I could do alot with that much money...
just build a nice 306 and a t5 with 9'' rear 306 about 1100 for a rebuild crate engine about 1300 for T5 and all the parts to install it 9'' housing from member on here 300 ish new 9'' third member 600-1200
Depends on what the car needs... could do floors, paint, etc.... first things I always do with a new car is upgrade suspension/steering/tires. Then do whatever you think the car lacks.(power/cosmetic)