I ordered my Dodge Dart Sport from the dealer back in 76 but as a slant 6 back then...it seen one and only winter that year and then got upgraded to a 350 hp 360 and got back to the road in 2009.
I put my Dart Sport away for another winter season this past week but I had to replace the orange box on the inner fender first, at least its a whole lot better than a complete overhaul.
Did your son ever think of a built up Mopar 360 like I have, it has about 350HP and 3.55 gears in the rear it is not a slouch and will make you feel the back of your seat.
I run 205/70x15 on the front of my 76 Dart Sport with no problems, might have to raise your front end a bit for tire clearance but driving it is the only way to find out.