Jo-Han never did a decent Cadillac engine. All of the Eldorados have Olds engines, and the standard Cadillac kits ('70 was the last one) used a simplified engine based on one they tooled for the '63 kit ('59-'62 annuals didn't have engine detail).
Someone with a shrink wrap rig pulled a fast one with the '70 in a '73 box. Jo-Han did stick later kits into the '72 box but the '73 is pretty tough to find in any form.
--Mark