Hi Todd, I think you'll find the 355/carb swap harder than fixing a TBI motor. TBI is pretty simple to troubleshoot.
Pull the air cleaner off and check the spray pattern from the injectors. 10psi is within spec but a little low. Spec is 9-13, TBI likes it closer to 13.
Test your coolant temperature sending unit:
http://67-72chevytrucks.com/vboard/s...d.php?t=425788
If the CTS sends the wrong info to the computer, the computer will try to adjust and may run rich or lean.
Test your throttle position sensor:
https://www.youtube.com/watch?v=l30-TNXj9Qc
Test your distributor module. You can remove the module without removing the dizzy. Most auto parts stores can test it for you.