My personal, somewhat unscientific, opinion is that the IPD header is a good replacement for a cracked manifold, but is not particularly tuned -- more of a cosmetic "upgrade." It's a 4-into-1 with a very short collector. A plus is that it fits without any clearance issues.

The VPD header is a Swedish 4-2-1 unit, which is also available from KG Trimning and Unitek (there are 5-6 models available to match your tuning needs). John Parker has them coated and has a bung for an O2 sensor fitted after he gets them from Sweden. You might inquire about the cost of buying one without the bung and in the original white transport paint -- it sands off easily and then you can apply the finish of your choice. Not sure if John is importing more than one model at this time; he may be. Some of us have had problems with these clearing the lower bellhousing support (easily fixed with a little grinding or hacksaw work on the support), or clearing the floor on 122 and 1800 cars -- have not seen this on a 140. That is easily corrected by a good muffler shop.

If you are planning on spending the money to have head work done, I would think you'd want the header that actually enhances performance most.