I do not have the link for you now, but right before the current class started, Joel took a bunch of pictures of how he assembled his first Street Rod. I think it was based on screws into the sides of the wood chassis fitting into balsa pockets in the car body.
Some others have used velcro connections between the two main pieces and that seems to work. I started and so far stayed with a more elaborate system, that is still fairly light weight, with little plastic nuts super glued to bitsy pine blocks mounted on the underside of the car body. I then screw the wood chassis to the body and have a little slop in the wood holes to allow for alignment adjustment.
Whatever you do, it takes some work to get the chassis mounted to the body at the right height for wheel clearance. I suspect there are many ways people are doing this, none are very hard, but all will probably take a little time for your first attempt. It's kind of like making fenders the first time, the first time takes a while longer and you REALLY want to see it run down a track before you send it in to make sure that you have accounted for wheel position when the chassis is weighted, etc..