So...

Maybe use jacks and jack stands to raise it off the frame high enough to get I-beams or 4x4 under the body and between the frame side to side. Support the 4x4 to the body with more boards to spread the load. Then ropes/straps up to the crane. It may be a good idea to reproduce the lifting points above the van to ellininate the ropes/straps from comming in contact and damaging the body. Or throw jack stands under the 4x4s once you get it off the frame and drive the frame out from underneath it.

you should just realize you fail and have buttsecks with the owner's daughter

Lol. I’ve done crap like that. Put trucks on frames of other trucks. Made trucks from other trucks. Made cars from a combo of cars.

A friend got his Camaro t-boned in a wreck and sold it to a guy I know. The guy who bought it wanted me to rebuild the engine in the wreck and put it in his car. Then take the drivetrain, trans and rearend out of the wreck and replace his. My friend had a shift kit in his tranny and a 12-bolt rear-end in the wreck.

Then another guy wanted me to take the body off his Pontiac and put it on another frame. I think I rented an engine host to do that job. It’s been like 15-20 years ago since I did that job.

Maybe get everything loose, rent an engine hoist, lift up the body in the front, block up, then the back, block up, then roll away frame. Now that I think about it, I think I used a big oak tree to help do all this. i got it done somehow.

Hey, that’s how to do it!! “somehow”