Header Size Recommendation

Re-read your post. If you actually have a 3500 converter and 4.10 gears you could use the 5303's and make more power. That is a 1.875 tube, 28-30 inches long. The early headers had 3.5 inch collectors. The later ones had 3.0 inch headers. The current set I have came with a 3.0 inch collector. I bought some 3.5 inch collectors and use those.

The 5204 is 1.750 tubes.