Look I'm a noob so dont hate. Headers questions...

[84Longbed]

I got some headers for my truck, seem to be round tube where they meet the manifold. The 84 Scottsdale came with a 305 but now has a 350 in it. Im unsure of what year the motor is, but is there another way to tell if my heads have round or oval ports(short of pulling the manifold)? On the other hand, I read that the port difference wont matter as long as the pipe on the header flange is bigger than the port on the head. Is this true? Hoping to knock this out tomorrow so I'd be very grateful for fast responses. Thanks