Can I use a weber carb on my 1965 spitfire
don't know much or how to rebuild su s so I would like to put a weber on the car
Then I suggest you find a shop and have them rebuilt and setup correctly, changing to another brand will require some modding and internal adjustment to get it to work and even then you may have difficulties. I know sometimes replacements are necessary but try to keep it stock when you can as it was designed to use the factory setup.
The big bore Webers are too much for your little engine. SU's are great carbs and not hard to rebuild.
Conversion kits. I probably would not use this unless I added a cam, head work and headers. https://rimmerbros.com/Item--i-RL1687--SelectedCurrency-3?gclid=EAIaIQobChMI7p_F- 5236AIVidlkCh1S2wN_EAQYASABEgJyD_D_BwE