Keep the poly and learn to get it running right, it is ideally suited for a low budget college student. Reliable, economical and tough. A later 440 smog engine is going to be a dog that gets horrible fuel mileage unless you do a full rebuild with high compression pistons, a better cam and high performance exhaust. Most of the late model 440's for sale these days are recycled motor home engines that were built to push a big motor home with loads of low compression torque but little top end performance.. That late 440 will motor the car down the highway but as a college student, can you afford 8-10mpg on ever increasing fuel prices?
Putting on my old racer hat, the '65-'66 plymouths were good candidates for high horsepower conversions, tough unibody construction and relatively light weight. Save the car for a later high end performance project. Once you finish college, if you still have the urge, that will be the time to tinker with building a high horse monster.