Stalls on idle in gear

if the mixture screws have no effect on the idle then the primary side is open to far need to turn carb over and open secondry side until you see the transfur slot this will let you pull fuel out of the backside let close the primary side and your mixture screws work will help idle and stalling

I missed the mix screws not doing much. That is usually an indicator of not enough initial timing causing too much throttle blade opening. Guys using the total timing method usually fall into that hole.

I wouldn't mess with the secondaries yet until you have a known initial timing setting that is adequate for the cam/engine. Until then, messing with the carb is a waste of time. XE262-268H are usually in the 14-20 range depending on the engine and that's similar to what he think he has in the engine.