im sure with all bolt ons, cranked up timing, custom or performance cams, performace head components.. valve springs, valves, tappets etc, and with race fuel its very possible, but 300HP is virtually unattainable for everyday reliable driving.
with a 2.8L the way to go would be s52 cams, OBDI ecu, exhaust, injectors, m50 manifold, CAI, and headers... that would probably put you at around +- 250hp.
With FI you would be SIGNIFICANTLY lowering the life of your engine if you run stock internals. FI probably wouldnt be the best choice for a DD.