Re: #3 Exhaust hotter by 130* ?????
Had a similar experience on a fresh-fired 496, except it was #8 running hotter than the others (about that same amount). It was being caused by a leak at the vacuum distribution fitting on the intake manifold. Dumb oversight on my part, I had hooked up all the lines except the one to the Cowl Induction diaphragm (hood was not yet on the car)
That cylinder may be running lean, I would check all vacuum sources and if that's all good it might possibly be leaking at the manifold sealing surface at that port.
1971 Chevelle SS LS5 Lime Green/ Jade
496 TH400 4.10 rear
Track times pending
1987 Buick Grand National
11.60 ET 88K stock long block with bolt-ons