Well its not work if you like doing this stuff.
But It down right sux if you need it ASAP.
Either way I would say installing the TBI would be harder.
Here is what I did.
I put a SB carbed400 in place of a TBI 454 .
The motor came out of a 1980 C~30 Camper
I used the Motor Wiring Harness except for 1 connection it bolts right in .
so you will have to check to make sure all the wires correspond the same.
Fortunately the Computer thing was sort of a after thought on GM's part
Most of all the TBI stuff goes in or out of that big hole on the Passenger side of the fire wall.
I removed the ECM & all the wires going to it..
You will need to drop the fuel tanks Remove the fuel pumps & extend the pick up tubes. & disconnect the power going to the fuel pumps.
I can not think of anything else right now but I am sure I missed something. I am going to flip thru the couple thousands pixs I took during the job