I don't have a clue about part #s...I have multiple parts guru's in my building who deal with that sort of thing. The issue I had with just welding the perch onto the existing apron vs. the new kit with the apron section, is that the new part is fool-proof to locate properly and has a much larger surface area where it is tied to the existing structure. We work on new 5-Series BMW's with the aluminum riveted-on front structure and have seen how strong these special rivets and structural adhesives are. In my experience the cars with rusty perches are few and far between, although I suspect that varies regionally...farther north, more prone to rust. Additionally, the cars we have seen with bad perches are visibly rusty, with the wheel off.

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2002 Ford ZX2
2 x 2013 Honda Civics