[2.70Racer]

Erik,
60 idle jets may be a bit big for your application. 50-55mm will be closer.
Further they should be checked. A 60 idle jet is 0.60mm dia. or .024"
It is common to find these out of spec. Usually larger than marked.
With older carbs, the shafts are worn and leaking air. These worn carbs will not idle properly.
Any perceptible motion from the shafts will leak air. Fix this first.
The main jets, if they are 145, should be fine. They really play NO part in the idle.
To check the mains the dia s/b 1.45mm or 0.058"
Another fairly common problem with old Webers is leaking O-rings at the idle jet holder and at the idle mixture screw. These carbs after all are typically 20 years old or more.
I assume you have the carbs mounted on the insulators. If not the carbs can and will percolate.
Float height is best determined with the sight glass screwed into the side of each bowl and running. This will show you the actual running float height.
PMO knows how important this is and installed a sight glass into each PMO bowl to see at a glance the float level.
The sight glass float bowl tool may be available from Pelican.
Fuel pressure s/b 3.5 psi. Again a permanent gauge is best.