Externally the two engines are the same (116.96x).
For swap purposes use the complete flywheel triggered ignition system (including the distributor) from the 88 420, and the complete injection system from the 83 380.

If you use the 88 injection system (KE-jet) there will be additional wiring harness work and a change of the ECU.

Thank you, Frank!

Exactly the kind of info I was looking for. Since I have the complete donor car with harness & ECU, etc>, it appears to be doable.

Now let's see if I can pick up the 380SEC for the right price?

Thanks, again!

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'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435

One further point: if you use the 88 KE-jet system, the fuel pumps (two), filter, and accumulator will be required, as the system pressure is higher than in the 83 system.