Newbie with cam and timing question

[Beej]

I'm new to the site, I introduced myself in the Welcome Area, My name is Ken. I have to admit it has been a long time since I have torn into a Chevy 350, so... the story goes like this...

I bought this 1975 C10 for my son and I to work on, it's coming along nicely. It has a 1977 350 engine that has been rebuilt by a reputable shop. It has an Edlebrock Performer 4bbl and intake with Flowtech headers and 40 series Flowmasters. We decided to put a reground 270 cam in it. Specs. are; Dur Deg @ .50 Int. 224 Exh. 224, Valve Lift Int. 467 Exh. 467 Grind is #270 (hence the name) and the cam number is #274.

I assumed that it would be installed just like a stock cam and lined up the crank and timing gear marks as stock, crank at 12 o'clock and cam gear at 6 o'clock, right? Well, after getting it all back together and the distributor in the right place, I adjusted the valves, also as stock.

Here's the problem... When we started it... it started right away but idled at about 1600 rpm and we couldn't bring it down at all and it got real hot real fast... headers got red... Tried to set the timing but when I turned it back it would just die... Any Ideas? Would valves being too tight cause this? I haven't adjusted valves in many years and may have got it wrong. I tried rotating the distributor 180 degrees but it just backfired so I must at least have that right.