1998 360 Magnum or 1965 273 cu in

Id keep the 273. You can perk them up but won't have the tire shredding torque of the 360. Your wheel arches are pretty narrow for any tire back there and the 273 with its manifolds sits nice in there. You can go magnum exhaust on the 360 and clear most everything under there but you still have to make downpipes for the magnums, deal with the balance issue and clutch size as well as the intake. You could do alot to the 273 with all that 360 money.....including hydraulic lifters....heck throw the rollers in there on a 5.2 roller cam! Make a spider retainer for the lifters.