performance for 84 GM
That 84 has a 302 with Throttle Body (TB) Induction. Low 16s? Mid 17s is closer to reality.
The two biggest improvements are gears and exhaust. That car has the same 8.8 rear that's found in the Mustangs, and probably has 273 or 308 gears. A switch to 355 or 373 would feel like you added 50hp. Stay with 355 if you do a lot of expressway driving.
Mustang "shorty" hedders will fit. They exit at 2 1/4". Run 2 1/4" thru 2 1/2" cats, back to 2 1/4 exhaust pipes, H-pipe in stock location, 2" tailpipes. A new fitting for the O2 sensor will have to be made, the wire extended about 6". Elimination of the O2 sensor will cause irratic running.
TBs operate on about 11 psi, waaaaay too much for a carb. If you change to a carb, the pressure must be regulated down to about 4psi. Edelbrock is a good choice. The factory aluminum 4bbl intakes can be found, for about 1/2 the price of a new Performer. Stay with 600 cfm or below.
Last, but not least, a cam change, along with a double roller timing chain, and fresh, stock heads will really make a diff.
With all the above "stuff" and proper tuning, you should dip into the very hi 16s to 17 teens at about 81 mph.
This is a good number for that 4000# sled.