The Grand Prix is it's own entity.
He's discussing modifying the stock HS/VA-50 Subframe to accept a swinging french motor.
My assessment: It could work, but you are going to end up doing a LOT of fabrication to rebuild the mount location and make appropriate clearancing for the spring and carb which is now directly in the way of the stock subframe.
IF you are looking for a project build, do it.
If you are looking just to replace your motor for ease of parts and maintenance, it may just be easier to keep the M48 going.