Will NOT run right!!!!!!!!!

Got a new guy question here. I'll try to give as much info as I can. Got a 74 dart custom. was a 225, swaped in a 318. Has a new holley 600 vac sec., performer intake, comp xe250 cam, 9:1 pist., factory heads w/hard seats, fact. crank and rods, factory dist., accell coil standard ign. box. I've built a hundred of these for other people so I finally did one for me.
PROBLEM: the car runs and drives great, gets good gas milage....but when it comes up to operating temp., it starts to miss. Sometimes it will be driving fine and when I slow to turn into my driveway it just shuts off. It starts right up every time, but just doesn't want to run right.
WHAT I"VE DONE: changed coils(twice), changed dist., new vac. adv. canister on dist., changed ign. module(twice), had alternater checked-working perfectly, cleaned ALL contacts and grounds in wiring harness and ign. parts, Put extra ground cable from engine to frame, changed ign. solinoid(relay), checked mainfold and carb base for vac. leaks..no leaks, no gas tank problems, put on a new gas cap(vents perfect), charcoal canister vent line not clogged(blew air through it), no melted wires or spark jump, spark plugs all look good-carb set great.
What gets me is it only does it when its warmed up, so some of these things I knew weren't it but you have to check anyway. The only thing thats got me curious is this car has the ignition reset button under the hood. I normally unplug the front seat from the harness and I'm good to go, never had any problems like this before so don't know why they would start now.
Anybody have any experience like this? Ready to pull the remaining hair out of my head. Thanks for any help. :banghead: