cat and carb replacement

[Michael Jose <mwjose@u.arizona.edu>]

In search of passing emissions, I now find that the cat is useless and
the carb so messed up action must be taken
Is replacing the catalytic converter a simple job, or must i hoist the
engine etc.?
I want to replace the carb, what should i go with?  another ZS?  the
replacement SU for single carb, a weber, or dual SUs?  What is easiest
and most likely to be able to pass emisssions?
TIA for all the help.
Mike