IMHO, 260* @ 50 seems like an awfully big cam for a 383 with iron heads. And you say that this is a smaller cam than you had before? 140 cranking does sound low for that big a cam. For comparison, my last 500" wedge had a 250* cam, ported Eddies, and 180# cranking compression. That combo had a bumpy idle and wanted a lot of lead at idle. I usually had 28* at idle. It wanted more, but would start hitting the starter when hot any higher than that.