Help needed!

If you are looking for an engine like that.
Check ebay at ibson engines or like that.
They are resin engines. Or scratch build..

Well the big block Chevy is easy. If you don't get a resin engine like Gibson, pretty much any '68 to '74 Corvette kit has that in it, even the '75 to '77 kits have them, although the real car didn't have them after 1974. The serpentine belt and accessories I don't really know at this time.
The Revell '68 Corvette Roadster, kit# 85-2544, has the engine and is pretty plentiful and cheap. Micheal's usually still has these on their shelves and you can use their 40% coupon for it, if you have Micheal's available to you locally.
The AMT C1500 454SS truck kit has a big block also, kit #6032, although I don't know how detailed the engine is, it should have that serpentine belt setup on it, but probably won't have headers for the exhaust.