Doug’s Headers makes pretty sweet stuff. I’ve used them multiple times. The newest are these 1-3/4-inch headers with 3-inch collectors for 1962-1967 Chevy IIs and Novas.

Here’s the officlal release:

New from The original DOUG’S HEADERS, the
D317 tuned long tube header is engineered to fit 265-400 Small Block
Chevrolet engines in very confining engine compartment environments and
still gives the maximum ground clearance possible. Designed
specifically for 1962-67 Chevy II and Nov

These headers are built with 3/8” thick flanges at the cylinder head
and 3 bolt outlet flanges. The 4 tube under chassis exit design is made
from 16 gauge tubing for durability with 1 3/4” primaries and 3”
collectors for increased horsepower and torque throughout the
powerband.  Designed to work with automatic transmission cars equipped
with power brakes, power steering and air conditioning.

They come standard with a polished high luster heat and corrosion
resistant metallic ceramic coating for a rich appearance and long
life.  These headers come complete with reducers, 1100º F rated gaskets
and premium installation hardware and instructions.  Headers are also
available uncoated.