'79 and later 250 had the Pulsair head with integral intake manifold and 2bbl carb.
The 292 and earlier 250 and 230 with separate intake manifold and exhaust manifold used a one-piece gasket, but there is a three piece gasket available.
Felpro's intake gasket has their Blue-Line. The two piece exhaust has a separate part number.
http://www.summitracing.com/parts/FEL-1257/
http://www.summitracing.com/parts/FEL-1448/
I tried these gaskets when I first put the headers on my 292.
THE GASKETS ARE CRAP. At least for use with headers. The exhaust lasted a week. They are crap and overpriced.
Felpro does have a one-piece, but is for stock cast exhaust.
The end studs are threaded into the head. Soak with your favorite penetrant for a day and turn out with a good vice grip with good sharp teeth. You would be doing yourself a favor if you install studs in all the manifold bolt holes.