Why not just glue the body halves together and cut off the cowl? That is how I did my Ramchargers and More American Graffiti cars. Then you can do the chassis in one piece with out messing with the roll bar hoop or trying to get rid of the body seam after you assemble it around the chassis.
Yeah, the early cars where not short! Maybe AMT made the kit before they could actually measure it. But then again, most funny car kits where a bit weird at first. Just look at Revell's early stuff.
I would love to have this kit as well