Was driving to work this morning when my truck took a dump on me. Started up fine, drove about 4 miles and then felt it start missing and loosing power. When I stopped, the idle was very rough and then it wouldn't idle at all. I did manage to restart it a few times, but had to keep my foot on the gas to keep it running (rough). The exhaust now emits white-ish smoke-not steam. The truck had been running great up to this point Here is some background: '72 350 cid short block, Edelbrock Performer intake #2101, Edelbrock #1406 600 cfm carb, Mallory Unilite distributor. I just installed Edelbrock heat insulator gasket #9622 (I think thats the number) between the carb and the intake to eliminate fuel percolation. In the past few days, the engine has been "running on", or dieseling after it has been turned off which it never did before (it did this before I installed the heat insulator gasket). I have run the gas tank down very low a couple of times recently, so I thought that I might have sucked up something from the bottom of the tank and clogged a filter, but the symptoms don't seem to match. I have not had time to check the filters, distributor, carb, etc yet, so I cannot elaborate any more right now. ANY help, opinions, suggestions would be greatly appreciated.