The 1960 Desoto was a unibody. Use the Lindberg/AMT 1964 Mopar chassis, engine compartment and suspension parts. The wheelbase for those kits is supposed to be 118.5" but measure out to 119 scale inches/119 mm. The '60 Desoto had a 122' wheelbase but the Lindberg chassis work and the wheels line up center of the wells without any chassis hacking required. If you check ebay, Model Car Mountain and others usually offer the interior, chassis and suspension trees for around seven bucks. Also, the Lindberg interior tub and panels can be used to place the Johan tub inside so everything lines up and is secure. The door panels can be reversed so that there won't be any obstructions interfering with the Johan tub. To correct the shallow Johan interior, you can carefully remove the floor areas of the Desoto tub and add a 5 mm styrene strip to the bottom of the door panels and the front bottom of the rear seat and the lower front and rear of the front bench seat. When the Johan tub is inserted into the Lindberg tub, the styrene strips will abut the floor of the Lindberg tub and will give you the proper depth.