Rebuild or replace?

Can a 273 be made to be a strong runner , sure it can, but for most they would be better off going with 318/360 even for a mild engine.

For most setups a 250hp 360 or even 318 will walk away from a 250hp 273. A stock magnum 5.9 with 4bbl and headers dynos 320 hp @ 4800 add a mild hydraulic roller cam and be at 350+ hp @ 5000-5200 rpm max.

Be very street friendly get away with any gears or stall, even though a step up in both would help. Little reason to build anything less then the need to be different.

I’m all for people doing /6 273 could arguably throw 318 into the mix. But for most a even if power isn’t a huge concern would be happier with even a dead stock 2bbl 360 over anything less.

Not to get into "Bench Racing" but A 360 with 250 HP would be a low rpm tractor motor. A 250 HP 273 would be a High Performance motor. The 273 would win no problem. Plus by changing motors, the OP is replacing everything in the drive train when he does not need to.