Can a chevy 305/700R transmission engine from an 85 Persianne fit into an 87 El Camino?

What engine does the Parisianne have? If it is a Chevy engine then that 700R will bolt to it. If it is a Pontiac 301 then the case would have the wrong bolt pattern. I do not think that the 700R was ever built with a "dual pattern" case ( like the 200-4R). Another problem will be a transmission cross member, this setup will take a special cross member since the 700R has a different trans mount location. You will also be required to shorten the driveshaft as well as change the yoke to one that fits the 700R. This is not an impossible swap, however it does present some substantial problems to overcome. A 200-4R is a better fit and will give you a better gear ratio as well as bolting directly to the 305 in your El Camino. The only major change with the 200-4R is the cross member, and you can find those in some salvage yards for about 1/2 or less than the cost of an aftermarket piece.