Need advice about Ford vans

My trusty '82 Ford cargo van is coming to the end of it's days. I've got a line on a nice used '94 E350 XLT passenger van. It's the standard length with quad captain's chairs and one bench seat. My dilemma concerns the rear air option and it's effect on the vertical clearance needed for the bikes. The rear air duct work runs down the center of the roof to what looks like a plenum that occupies the space just above the rear doors. Without the duct hump, my bike should fit fine. The carpet-to-hump distance is 50" inches (in contrast, my E100 cargo van has a 53.5" floor-to-ceiling distance) and I'm concerned that both the plenum and the duct are going to be a problem. My bike is just a bit over 50 inches at the bars. I don't want to make an offer on the van until I sort out what I want to do about this.

One thought is to use tie downs to compress the forks, but that seems like a pain in the rear if you have to do it on a regular basis. The other thought is to remove the ceiling headliner and air ducting for the last two thirds of the van. Is that difficult to do, or is it a bad move. Would it be better to keep looking until I find one without the rear air option? I can't be the first to confront this problem, so I'm turning to you, my DRN brethren, for advice and comment.

Thanks.

I don't know anything about the system, so I can't say whether there's another evaporator. That would complicate things. Maybe someone here who has one of these can tell me. The rear plenum is about six to eight inches wide. I was planning to cover the carpet with a rubber mat, but I suppose it could come up if that would buy me something.

Thanks guys. Unfortunately, the owner had a change of heart at the last minute and pulled the van off the market (I think a relative decided he wanted it). That's the way it goes sometimes. I'm back at square one and looking at want ads.