Slant six Holley 2280 stalls when stopping

Got the new chinese carb yesterday and after a bit of effort to get fuel into it, the old girl is running very well.
It was idling at 300 rpm as I was getting a screwdriver to turn up the idle.
It was running at ~700 rpm great so will get it set in gear now and take it for a run.
Thanks for all the help and wouldn't you know it would be the gross failure and not the little ones.
Keep your fingers crossed that she runs well and doesn't take a dump with the new off-shore carb.