Trying to Gauge Interest In Some Parts
Not trying to add fuel, but I agree with the OP that the J-pipe adaptor setup is likely not the kind of project to get involved with. It sounds like he is looking for something small and machined. All the components are already available to make a J-pipe for a turbo. A complete turbo header is the unfilled product. If the end user has to weld it together themselves then why should they go to the OP to get the parts when they could just as easily buy them from a vendor themselves. And there are many varibles found in slant powered cars such as power steering, 170 vs 225, turbo size, or k-member clearance that would require the OP to have access to multiple cars for test fitting purposes.
Here is a quickly found source of pipe and flanges. I only performed 1 search without any price comparisons. Cut to length needed with hacksaw and weld on flanges, done.
http://www.summitracing.com/parts/vpe-2605/overview/
http://www.treadstoneperformance.com/view.phtml?f_cat=Turbo+Flanges
I am in the process of building a turbo header for my valiant. It will be a short tube setup that I hope will take up only slightly more room than the factory manifold. It will be an all stainless tig welded unit made from weld els (in the treadstone link) and schedule 30 304 stainless pipe. The header flange is available on ebay in 1/2" mild steel or 304 stainless.
I have to agree with you; the reasons for NOT doing this project seem to outweigh the reasons for doing it.
I thought that the CNC method of manufacturing the flanges would have the advantage of incorporating a configuration that would include a mounting "sleeve" that would encompass the J-pipe on both ends that would make the welding process easier (ostensibly, the J-pipe would already be cut to the correct length for the application and would just slide into the flange-sleeve, be rotated to the correct angle [supplied by reference marks, put on at the point of manufacture] and welded with no measuring, trial-and-error cutting and fitting necessary, a time-saving measure for the customer.) The J-pipe would, of course, already have been cut to the correct length by the "kit" provider.
This mounting-advantage afforded by the "sleeve" is unique, and not available on any of the readily-obtainable flanges that I know of. The "sleeve" would only have to be 1/2"-deep, or so, to be effective, but would need to be on both of the J-pipe flanges for the most advantageous usage.
Not trying to knock holes in YOUR argument, because I believe that it is a very good one, but I am not sure that the situations you mentioned insofar as requiring different physical combinations are all valid. For instance, the K-members are only going to vary insofar as height, I believe, with 170 engines having less vertical room than 198 and 225 motors. It is arguable, though, as to whether a "170 kit" would even be necessary, seeing as how most folks would agree that a normally-aspirated 225 can make about as much power as a turbo'd 170, and is a whole lot easier to build. I do agree that the power steering issue is likely to be a sticky one in terms of fitment, and would surely be problematic, with time spent getting the right length on the J-pipe a factor, and probably more... It may be that this "kit" idea just won't work at all on power-steering equipped cars... we'd have to ask PISHTA on that one.
Depending on the customer's own fabrication skills, this "kit" might or might not being a good idea, on second-thought.
The flanges, themselves, might be small enough to appeal to the friend of the OP, as a manufacturing project and when the advantage of the "sleeve" (with a shoulder at the bottom, to preclude over-insertion of the J-pipe and the reference marks to ensure correct orientation, with no time wasted (by the customer) on ascertaining proper placement of the J-pipe, prior to welding, and no time spent on internet searches and the time spent dealing with several parts sources to build your own "kit"... if your time is worth anything at all to you, this "kit" might have a fighting chance as a way to go... after all, the CNC flanges should cost less to manufacture (and therefore could be sold for less, as part and parcel of the "kit." than the ones off e-bay or from another supplier.)
But, overall, you're probably right; it's probably a bad idea...
We built our own header (on a different subject, now,) and spent a cool $1,000.00 doing it, since we had to pay someone else to weld it and had to take it 130 miles (one way) to get it coated (two round-trips at a time when gas was about $4.00/gal.) I am very much interested in both your engine and your header. Could you post some pictures, please? We're new at this so, are (obviously) still learning. Pictures help... a lot.
Thanks a lot for your insightful, pertinent, comments and your interest!!!