Maybe my problem is similar to yours. I have a 360 and 4 speed in my Duster, 292/508 cam, Victor 340 intake, block .030 over KB 8.66 comp pistons, '923 heads milled .020, NEW Holley 750 VS TTI headers and factory electronic ignition. Mine idles fair, (not bad for a lumpy cam) but will bog and stall for no reason. I can slip the clutch and put around, but when I lean into it, it also bogs and stalls. It is getting a healthy accelerator pump shot. In the past, I have found that when an engine stalls under a load , the problem usually lies in the ignition system. I had a slant sick in a 77 D 100 that did wouldn't go over 29 mph. I tried everything, THEN swapped in a known good used distributor cap and plug wires, and it was finally able to peel out and break the speed limit. I am going to try another set of plug wires in my Duster tomorrow. Good luck with your project!