When I had to get mine engineered they gave me a list to chose from, not just any mechanic can do it, pretty sure it's a qualified mechanical or structural engineers job.
I used a guy in Willetton probably 22 months ago & he was great...$400 from memory.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.