Bryan, will you be at Lime Rock over the 4th? If so, look me up in
the B paddock. I have a decent collection of mains and jets. Also I
run the opposite almost...i.e. instead of 145 air jets and 165 mains,
I would have 145 mains and 165 air. Do your plugs look like what you
would expect based on the EGTs? I've seen where EGTs read lean when
the problem is the motor is really so rich it's burning fuel in the
exhaust pipe. Sometimes the EGTs aren't always giving you the
information you think. You may need to look at several things to get
the full picture. I do agree with the others, though---check the
valve springs first. If any are broken, you will have problems
getting the revs.

As to your question regarding flats vs Weber changes, the answer is
the dreaded "it depends". The Griffith carb was very sensitive, so
two flats there could be a change of 10 on the mains. The Ellis and
Comptune carbs were far less sensitive. A change of two flats there
might only be a change of 5 on the air correctors, if anything. I
have no experience with anyone else's SU carburettors on a production
car. Call or email me if you have more questions on this, I'll help
if I can.