Welcome. You are right, the 1964 and 5 273 manifolds don't bolt up to 66 and newer heads. The bolt size is different as well as the angle. The holes can be modified and angular washers used to make it work. There are numerous threads here on the site about that. I must correct you about something, The never was a "Super Commando" 273. Dodge called their 4 barrel engines "Charger" and Plymouth called theirs Commando. Both were 10.5/1 compression with 4 barrel intake and carb, a slightly larger solid lifter cam, dual point distributor, special valve covers, a chrome unsilenced air cleaner, and special large single exhaust with a square resonator tip. In 1966 Dodge came out with a D Dart that had a modified 273-4 barrel engine with 275 horse for NHRA's D stock class.
Welcome. You are right, the 1964 and 5 273 manifolds don't bolt up to 66 and newer heads. The bolt size is different as well as the angle. The holes can be modified and angular washers used to make it work. There are numerous threads here on the site about that. I must correct you about something, The never was a "Super Commando" 273. Dodge called their 4 barrel engines "Charger" and Plymouth called theirs Commando. Both were 10.5/1 compression with 4 barrel intake and carb, a slightly larger solid lifter cam, dual point distributor, special valve covers, a chrome unsilenced air cleaner, and special large single exhaust with a square resonator tip. In 1966 Dodge came out with a D Dart that had a modified 273-4 barrel engine with 275 horse for NHRA's D stock class.