1998 360 Magnum or 1965 273 cu in

Two different animals. A 360 is a low rpm high torque motor. The 273 is a high rpm screamer. The 273 will act like a normal engine till it hits 3,000 rpm and then pulls hard though 6,000 rpm like a 340. The 273 will also get you 20 + mpg cruising with 3.23 gears. I would think the exhaust manifolds would work with Magnum heads, but there will be a lot of gotcha's, including balance, motor mount bracket, timing cover and everything in front of it, and you have small wheel wells, clutch to hold a 360 with the 273 flywheel. That's what I come up with off the top of my head. My brother and I both ran 273's for decades. They are great engines.