It could be, but there would be lots of fab. work. You will pretty much just have to "back half" the pan.  May be easier to just make a tube pan designed with mid engine in mind.  Otherwise you pretty much have to figure out where you want the rear wheels and measure forward on the pan the length of the engine and transaxle from the diff. Mark the pan and chop it off. You may be able to use many of the factory parts and set up the rear suspension with coil over shocks, that would allow for the removal of the torsion tube.  I would imagine you could do a setup like a formula V or a mid engine sand rail modded for a street car. Then you have to deal with clutch and shifter linkage.  Probably just a hydraulic clutch master and slave setup but getting a good shifter feel could be a little more difficult.  I've done it on a late model Corvair but thats apples and oranges..unibody vs pan based and the differential stayed in the "factory" location, everything else moved around it...still, lots of fab work to say the least.