Mike
There is a car that someone posted a pic of that was a "MK-IV" with a chevy engine. It had a replica tub. At one time someone tried to pass it off as real tub "J13" The tub was not honeycomb and there never was J13. J7, which was crashed at LeMans was restored with honeycomb and that was a very fine restoration that I'm willing to bet wasn't for free. The tubs of J1, J2, and J3 differ from the tubs of J4, J5, J6, J7, J8, J9, J10 and the two spare tubs that were numbered in later years. (Not by Ford J11, J12). It wouldn't be hard to make a replica MK-IV tub. I think it would be hard to make a composit honeycomb one that was exactly correct. Remember the Brunswick aerospace corp charged Ford $250,000 in 1967 for each tub. To prevent fake cars from racing in FIA vintage events (Some vintage races don't care and allow replicas) the FIA issues FIA papers to cars that they have inspected and believe to be real. Lee Holman is working with the FIA to certify the GT40s that wish to race in FIA events. I'm working with Lee in providing information on the J Cars. Their requirements are very strict. I don't think the wildwood brakes on JWhat's car would be acceptable to them. On one level who cares? As I've said I have great respect for any one who builds and enjoys any of these cars real or replica. If JWhat can prove this is J1 I be the first to admit it but up until now nothing convinces me that it is.