I have a pair of World Products SportsmanII heads to put on my car. The exhaust port openings are a bit larger than my existing 1 5/8" header openings. Think this will work or should I get 1 3/4" headers?

 

You could do that. Whether you need 1-3/4" for flow purposes depends upon the rest of your combo (intake/cam/displacement).

You definately don't want a sharp impingement in flow as exhaust is going out of the port, though. An alternative to different headers, which may hurt you on the low end, is to run a weld bead around the outside of the flange around each primary tube, then open up the flange openings to match the ports. Smooth them into the round shape of the tubes, and you'll eliminate the flow interuption problems.

I just finished doing that on the headers on the '57, in case you were wondering. It was a nasty situation - 1-3/4" round flange openings in the headers, 1-3/4" square exhaust ports.

Nasty, nasty situation.

 

I didn't even think of putting a bead around the header. Thank you for the input!
Any ideas on what intake would be for these heads. Car is mostly street driven. I think I would have to open up my weiand stealth intake.