Power Plant Upgrade Recommendation Request

[Elwood]

I have a ’75 Spider that I am going to convert to fuel injection. The existing ’75 1800 runs very well and has just over 100k.
My parts bin consists of the following;
Complete FI set-up (harness, dizzy, ECU, intake, AFM, relays, fuel tank, fuel pump, etc.)
Complete ’76 1800 engine
Complete ’80 2000 FI engine (harness, dizzy, ECU, intake, AFM, relays, etc.)
’80 cross member

I don’t know what condition the spare engines are in but my suspicion is that they are ok. Neither have been run for several years and both have under 100k miles. Here are the questions:
What is my best option with regard to block and head combination?
What is the best path to travel with the fuel injection installation? Do it on the existing '75 1800 and rebuild the 2l? Rebuild the '76 1800/'80 2l and install it along with the FI at the same time? Should I buy a vowel?
My main goal is fuel injection. The ’75 1800 pulls hard and is fine performance wise but I don’t like carburetor fussiness. Fuel injection just works.

Thanks for the guidance.
r/
D.

[So Cal Mark]

use the 2L block and 1800 head with the FI setup. Gobs of torque and great driveability