408 Stroker Spark Pugs and tuning

[Merc Dr.]

Just got my car back today from the tuner after the engine rebuild. 408 stroker, Vararam, 3200 stall, Livernois 2c cam, 11:1 compression. Couple questions though. Had a couple hard starts and was starting to wonder if the plugs should go up or down in heat range? Running stock plugs right now. I've also noticed it revving low when coming to a stop, kinda sputtering, almost dying. I know I might have to take it back, but wanted make sure I wasn't missing something else first. I haven't had a chance to see what the redline is yet either. I might have to have that bumped up as well. It was making 435RWHP

[Merc Dr.]

To answer my own question... After doing some research, I looked at companies like ATK and Blueprint Engines and found they were running/recommending the stock plugs.
The car is back at the tuner now. I have them bumping the rev limiter up to 7500. After taking a good look at the dyno sheet, I realized it was making peak HP right at the limit, roughly 5800RPM. I think there might be a little extra there. If nothing else, I want some breathing room to shift at the top end.
As far as it dying, I believe the throttle blade isn't open enough at idle. It was often hard to start when the engine was warm. Also, the trans tune was off a little as the engine was still bumping the against the brakes at a stop. I don't think that's right considering it's a 3000-3200 stall converter.
I'll update later in the week when I get it back.