I would drop a 318 in it its direct bolt in or pick up a running 5.2 I would not install a a slant. I would stick the 273 in a corner and do something with it later.( Hey, you asked )
OR hey put floors in the other one and have 2 OR sell one with the slant OR...so many options :)
P.S. I knew a feller who would power brake a slant and get the wheels spinning in a 71 Valiant.
