crotchety old man

I apologize for being wordy but I am trying to answer all the potential questions in advance. I am helping a friend with a recent purchase. The car is a '62 FI mostly stock. The problem is getting the thing to idle. Part of the problem is that it sat for nearly 20 years with leaded fuel in the tank and lines. We have flushed out most of the garbage and I have disassembled the FI twice now to remove all the garbage, it is presently clean. We have a LARGE fuel filter in the line temporarily while the rest of the garbage flushes out of the system. I do not know what engine is sitting in it but it appears to have the 30-30 camshaft in it. Back in the dark ages I built a lot of small blocks, a few with the Rochester FI but I have no familiarity with the 30-30. My cam of choice was Racer Brown, and I ran some pretty long bump sticks with the Rochester and had no idle problems. My question if anyone has an answer is does the 30-30 have an unreliable manifold vacuum at idle, which is screwing up the balance on the FI and causing the idle problems. I can get it adjusted out but as things change (ambient temp, engine temp, underhood temp, drive time, traffic etc) it dramatically changes the idle. I am right at the point of suggesting that we tear down the engine, rings bearings head rebuild for unleaded fuel and replacing the cam with the original '097. I found an '097 replacement on the internet, does anyone have information on how accurate a replacement it is? Thanks in advance for any help as it is quite irritating to have this thing in the garage and not being able to drive it without all the headaches.