450 holley help

ok, I have a 450 holley ( mech secondary ) on my 225. the short block is a re-ring/bearing with .120 milled off the block, little .465 lift erson cam w/222 [email protected], ported head with 1.70/1.44 valves. Aussie intake & Clifford headers, scavenger y into 3" exhaust. 904 trans w/2800-300- stall & 3.23 gears.

I know the 450 is probably not the best choice but, its new and its what I have.
the car runs decent, has some pep. I swapped out the metering plate for one with jets to help with tuning. timing is set at 30 deg. ( 20 initial - 10 mech. ) I have tried more & less this is where I get the most vacuum without any pinging. 15" max.

looking for advice/help to get the most out of this combination.
also looking to figure out why it likes to stall under 1000 rpm when coming to a stop.

pretty sure its something simple and stupid that I have overlooked.

Thanks!