This should answer all your questions (incl. the bolt angle):
Chrysler: 273 V8 thru 1965 Dual Quad Equa-Flow Manifold (5488)
[OFFY-5488] $516.15
Click to enlarge
1965 and Earlier Barracuda, Dart, Valiant 273 V8 Dual Quad Equa-Flow Intake Manifold
Works with AFB carbs only - No Holleys whatsoever, not even sideways.
Over fifteen years ago Offenhauser broke away from the old 180-degree and introduced a 360-degree design manifold which other manufacturers are now following.
You get full benefit of improved fuel passages on every single stroke, there is no down time with a 360-degree - your engine operates at full capacityall times. S0-called 180-degree manifolds operate on a part time basis due to the fact that one side of the manifold is down while fuel is delivered to the other side of the engine.
Exclusive plenum chamber design of Offenhauser 360-degree Equa-Flow Manifold wipes out flat spots in all RPM ranges. Gives you smooth . . . unrestricted fuel flow . . . continuously. Each cylinder receives equal fuel flow without interruption or oscillation. You get vibration-free smoothness and power rammed distribution through balanced efficency. Hands you more power off the line . . . a fantastic top end improvement. Dyno, Street-Strip Proven. Test results show a 20 H.P. increase at 6500 RPM over competitive manifolds.
Thru-1965, the 273 head had the intake manifold bolt holes drilled at a different angle than the other LA heads.
