All of what stampede said.
Carb is cheaper by far to upgrade. Plus easy to diagnose. You will need a distributor cause the one you have will be computer controlled. You need mech./vac. advances.
You need to pull the in tank pump. Way to much pressure for a carb even with a regulator.
However since you allready have the goodies for efi. I would work with it. The computer is a good idea. Have the heads been port-matched or anything. Are they stock 302 or 351 heads. Do you have an adjustable regulator and whats your pressure at. I think stock TB are 58-60mm. A little small for all that motor/intake and exhaust.
What gears/cam? Your setup would probably like to rev some. Damb that thing should be a rocket.
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82 Mercury Capri 302.
Comp. Cams
Tremec 3550
3.73's
12.8@106 N/A
Kevin's Capri