I sent you a rather long response yesterday, and now I find that it went away!!! Now I probably wont remember all of what I said. First of all, nitrous will work fine with any cam, not just big ones. Your cam is too big for the street, I know it sounds nasty and all that, but it is hurting your low end performance for sure, and it very well might be a big part of your idle problems. Something in the 234 to 244 or so will be much better. Lift should prob. come in at about .550 or so. I prefer a dual pattern cam, I think they do better with a longer exhaust duration for a BBC...they were never know to be very good on the exhaust side. Get it ground on a 108 if you want the nasty idle instead of a 110 LSA. I would dump the intake, use your Performer intake. A dual plane will be much better on the street. You will feel the difference, and it will be much better while warming up and at lower RPMs.. I'm the one who said that a 750 Holley vacuum secondary carb will do you fine. I have run many double pumpers on the street, and every single time I changed to a vacuum secondary carb, everything else being equal, the vacuum secondary was smoother and more responsive. And it took less messing with, idled better, etc. The Holley street avengers seem to be a good carb. I never used one myself, but have heard good reports about them. You can get the 770 CFM for your combo. Anyhow, I would go with the 3:73's, that's what I run. I actually wish I went a little more, maybe 3:42's or so...but the 4:11's on the street are bad news. On the timing, try 16 initial, make sure your vacuum advance is disabled and plugged. Big cams in big blocks like lots of initial. Just watch your total advance, no more than 36 or 38. Have it all in by about 3K. If you set your timing and idle, make sure the engine is completely warmed up first. Your idle problems are likely related to the big cam. You might have to either drill the primary butterflys, or crack open the back ones to give it enough air to idle right. But dont do that without checking how first! I dont know what cam you like, but if you want a name and number of the ones that have worked for me the best, along with the best service, I'll be glad to set you up with a phone number and contact names. You got a response on your other post about the carb sizes, saying they ran double pumpers on the street with no problems. I know others have also, but Im just relaying my experience with them, I have to say go with vacuum secondarys.