Idle problems sbc 350

I have a 96 vortec block, howards flat tappett cam, 480 lift-288 duration-108 center line, swirl port heads, dual plane intake,headers, and a new Edelbrock 600 carb.
I cant seem to make it idle high enough in drive without dieseling when I put it in park to shut it down.
I am pulling 15 lbs of vacum @ the port on the rear of the intake @ idle, and cant seem to find any vacum leaks.
I've been messing with the timing and idle screw and just cant seem to get it right.
KEEP IN MIND-This is an 1986 trk with a 1996 block and everything to do with the stock 305 is disconnected!!!

Isn't that a set up with a wire you gotta disconnect while setting base timing????

No I'm just running an old school HEI
The stock 1 for this truck you just set it @ 0 degrees, and the computer did the rest.
It had a large 4 or 5 pin connector that also went to the distributer that is now disconnected!!

IIRC--------it had to be set with some wire disconnected------------think it was a brown wire with a connector on the firewall to the right(passenger )side of the engine------------




and that was then the reference point for the ecu


found some notes----tan/black wire ------goes to pin D5 on ecm-------------look for single wire near dist area with a single connector

Hook your vacumn gauge up advance your timing to peak vacumn then back it off about 2" of vacumn. You probably won't get 20" @idle with that cam anyway.

You need an electric idle solenoid. You set your base idle with the solenoid. When you turn the key off it drops the butterflies fully closed and eliminates the dieseling.
All of the old late 60's thru late 70's cars used them. here's one for an Edelbrock carb. http://www.summitracing.com/parts/edl-8059/overview/