I would start with supporting mods so that some day you could step up into a V8. Just like tim said you could start with suspension, rear-end with upgraded gears & a posi, and then just the little things like a better air intake set-up.
If your dead set on keeping the 2.8 Im again also going to agree with Tim on doing a junkyard turbo set up. I have a few pictures of one and Im actually pretty impressed on how it was set up. Theirs plenty of space to work with too!
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